Method and system for battery protection

ABSTRACT

A system and method for battery protection. In some aspects, a method of conducting an operation including a battery pack, includes the acts of monitoring a first battery pack condition at a first monitoring rate, determining when a second battery pack condition reaches a threshold, after the second battery pack condition reaches the threshold, monitoring the first battery pack condition at a second monitoring rate, the second monitoring rate being different than the first monitoring rate. In some aspects, a method of conducting an operation including a battery, the battery including a cell having a voltage, power being transferable between the cell and the electrical device, a controller operable to control a function of the battery pack, the controller being operable with a voltage at least one of equal to and greater than an operating voltage threshold, the cell being operable to selectively supply voltage to the controller, includes the act of enabling the controller to operate when the voltage supplied by the cell is below the operating voltage threshold.

RELATED APPLICATIONS

The present patent application claims the benefit of prior filedco-pending U.S. provisional patent application Ser. No. 60/428,358,filed on Nov. 22, 2002; Ser. No. 60/428,450, filed on Nov. 22, 2002;Ser. No. 60/428,452, filed on Nov. 22, 2002; Ser. No. 60/400,692, filedJan. 17, 2003; Ser. No. 60/440,693, filed on Jan. 17, 2003, prior filedco-pending U.S. provisional patent application entitled “METHOD ANDSYSTEM FOR BATTERY PROTECTION” filed on Nov. 19, 2003 Ser. No. ______(Atty. Docket No. 066042-9536-00); and prior filed co-pending U.S.provisional patent application entitled “METHOD AND SYSTEM FOR BATTERYCHARGING” filed on Nov. 19, 2003 Ser. No. ______ (Atty. Docket No.066042-9538-00), the entire contents of which are hereby incorporated byreference. The entire content of U.S. patent application entitled“METHOD AND SYSTEM FOR BATTERY CHARGING” filed on Nov. 20, 2003 Ser. No.______ (Atty. Docket No. 066042-9538-01) is also hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention generally relates to a method and system forbattery protection and, more particularly, to a method and system forpower tool battery protection.

BACKGROUND OF THE INVENTION

Cordless power tools are typically powered by portable battery packs.These battery packs range in battery chemistry and nominal voltage andcan be used to power numerous tools and electrical devices. Typically,the battery chemistry of a power tool battery is either Nickel-cadmium(“NiCd”), Nickel-Metal Hydride (“NiMH”) or lead-acid. Such chemistriesare known to be robust and durable.

SUMMARY OF THE INVENTION

Some battery chemistries (such as, for example, Lithium (“Li”),Lithium-ion (“Li-ion”) and other Li-based chemistries) require precisecharging schemes and charging operations with controlled discharge.Insufficient charging schemes and uncontrolled discharging schemes mayproduce excessive heat build-up, excessive overcharged conditions and/orexcessive overdischarged conditions. These conditions and build-ups cancause irreversible damage to the batteries and can severely impact thebattery's capacity. Various factors, such as, for example, excessiveheat, can cause one or more cells within the battery pack to becomeimbalanced, that is, to have a present state of charge that issubstantially lower than the remaining cells in the pack. Imbalancedcells can severely impact the performance of the battery pack (e.g.,run-time and/or voltage output) and can shorten the life of the batterypack.

The present invention provides a system and method for batteryprotection. In one construction and in some aspects, the inventionprovides a system and method for monitoring the temperature of abattery. In another construction and in some aspects, the inventionprovides a system and method for transferring heat within a batterypack. In another construction and in some aspects, the inventionprovides a system and method for transferring heat within a battery packvia a phase change material. In a further construction and in someaspects, the invention provides a system and method for monitoring cellimbalance. In yet another construction and in some aspects, theinvention provides a system and method for controlling the operation ofan electrical device based on a battery's temperature and/or cellimbalance. In another construction and in some aspects, the inventionprovides a system and method for determining the present state of chargeof the battery and indicating or displaying a battery's present state ofcharge. In yet another construction and in some aspects, the inventionprovides a system and method for interrupting discharge current based onbattery temperature.

Independent features and independent advantages of the invention willbecome apparent to those skilled in the art upon review of the detaileddescription and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a battery.

FIG. 2 is a perspective view of another battery.

FIG. 3 is a perspective view of a further battery.

FIG. 4 is a perspective view of a battery, such as the battery shown inFIG. 3, in use with a first electrical device, such as a power tool.

FIG. 5 is a perspective view of a battery, such as the battery shown inFIG. 3, in use with a second electrical device, such as a power tool.

FIG. 6A is a schematic view of a battery, such as one of the batteriesshown in FIGS. 1-3.

FIG. 6B is another schematic view of a battery, such as one of thebatteries shown in FIGS. 1-3.

FIG. 6C is a further schematic view of a battery, such as one of thebatteries shown in FIGS. 1-3.

FIG. 6D is yet another schematic view of a battery, such as one of thebatteries shown in FIGS. 1-3.

FIG. 7 is still another schematic view of a battery, such as one of thebatteries shown in FIGS. 1-3.

FIG. 8 is still another schematic view of a battery, such as one of thebatteries shown in FIGS. 1-3.

FIG. 9 is still another schematic view of a battery, such as one of thebatteries shown in FIGS. 1-3.

FIG. 10 is still another schematic view of a battery, such as one of thebatteries shown in FIGS. 1-3.

FIG. 11A is still another schematic view of a battery, such as one ofthe batteries shown in FIGS. 1-3.

FIG. 11B is still another schematic view of a battery, such as one ofthe batteries shown in FIGS. 1-3.

FIG. 11C is still another schematic view of a battery, such as one ofthe batteries shown in FIGS. 1-3.

FIG. 11D is still another schematic view of a battery, such as one ofthe batteries shown in FIGS. 1-3.

FIG. 11E is still another schematic view of a battery, such as one ofthe batteries shown in FIGS. 1-3.

FIG. 11F is still another schematic view of a battery, such as one ofthe batteries shown in FIGS. 1-3.

FIG. 12A-C are still other schematic views of a battery, such as one ofthe batteries shown in FIGS. 1-3.

FIG. 13A is a perspective view of a portion of a battery, such as one ofthe batteries shown in FIGS. 1-3, with portions removed and illustratesthe FET and the heat sink.

FIG. 13B is a plan view of the portion of the battery shown in FIG. 13A.

FIG. 13C is a perspective view of a portion of a battery, such as one ofthe batteries shown in FIGS. 1-3, with portions removed and illustratesthe FET, the heat sink and electrical connections within the battery.

FIGS. 14A-E includes views of portions of the battery shown in FIG. 13A.

FIG. 15 is a perspective view of a portion of a battery, such as one ofthe batteries shown in FIGS. 1-3, with portions removed and illustratesthe FET and the heat sink

FIG. 16 is another perspective view of a portion of a battery, such asone of the batteries shown in FIGS. 1-3, with portions removed andillustrates the FET and the heat sink.

FIG. 17 is a perspective cross-sectional view of a portion of analternate construction of a battery, including a phase change material.

FIG. 18 is a cross-sectional view of a portion of another alternateconstruction of a battery including a phase change material and a heatsink.

FIG. 19 is a cross-sectional view of a portion of yet another alternateconstruction of a battery, including a phase change material and a heatsink.

FIGS. 20A-B are perspective cross-sectional views of a portion of abattery, such as one of the batteries shown in FIGS. 1-3, with portionsremoved.

FIGS. 21A-C are a schematic views of a battery, such as one of thebatteries shown in FIGS. 1-3, in use with an electrical device, such asa power tool.

FIG. 22 is another schematic view of a battery, such as one of thebatteries shown in FIGS. 1-3, in use with an electrical device, such asa power tool.

FIG. 23 is yet another schematic diagram of a battery, such as one ofthe batteries shown in FIGS. 1-3, in use with an electrical device, suchas a power tool.

FIG. 24 is a side view of a battery, such as one of the batteries shownin FIGS. 1-3, in use with another electrical device, such as a batterycharger.

FIG. 25 is a partial schematic view of a battery, such as one of thebatteries shown in FIGS. 1-3.

FIGS. 26-27 are graphs illustrating cell voltage and a ratio of cellvoltages over time.

FIG. 28 is a schematic diagram of an construction of a battery chargingsystem.

FIG. 29 is a schematic diagram of another construction of the batterycharging system.

FIGS. 30A-B illustrate the operation of the battery charging system asshown in FIG. 29.

FIG. 31 is a schematic diagram of a prior art battery.

FIG. 32 is a schematic diagram of a battery included in a furtherconstruction of the battery charging system.

FIG. 33 is a schematic diagram of a prior art battery charger.

FIG. 34 is a schematic diagram of a battery charger included in thefurther

FIG. 35 is a perspective view of a battery.

FIG. 36 is a top view of the battery shown in FIG. 35.

FIG. 37 is a rear view of the battery shown in FIG. 35.

FIG. 38 is a rear perspective view of the terminal assembly of thebattery shown in FIG. 35.

FIG. 39 is a front perspective view of the terminal assembly of thebattery shown in FIG. 35.

FIG. 40 is a side view of the battery shown in FIG. 35 and an electricalcomponent, such as a battery charger.

FIG. 41 is a schematic diagram of the battery and the battery chargershown in FIG. 40.

FIG. 42 is a perspective view of the battery charger shown in FIG. 40.

FIG. 43 is another perspective view of the battery charger shown in FIG.40.

FIG. 44 is a top view of the battery charger shown in FIG. 40.

FIG. 45 is a perspective view of the terminal assembly of the batterycharger shown in FIG. 40.

FIG. 46 is a perspective view of the inner portion of the housing of thebattery charger shown in FIG. 40.

FIG. 47 is an enlarged perspective view of a portion of the batterycharger shown in FIG. 46 and illustrating the terminal assembly of thebattery charger.

FIG. 48A is a perspective view of an electrical device, such as a powertool, for use with the battery shown in FIG. 35.

FIG. 48B is a perspective view of the support portion of the power toolshown in FIG. 48A.

FIG. 49 is a right side view of the battery shown in FIG. 35.

FIG. 50 is a left side view of the battery shown in FIG. 35.

FIG. 51 is a front view of the battery shown in FIG. 35.

FIG. 52 is a bottom view of the battery shown in FIG. 35.

FIG. 53 is a front perspective view of an alternate construction of abattery.

FIG. 54 is a rear perspective view of the battery shown in FIG. 53.

FIG. 55 is a top view of the battery shown in FIG. 53.

FIG. 56 is a rear view of the battery shown in FIG. 53.

FIG. 57 is a front perspective view of a prior art battery.

FIG. 58 is a rear perspective view of the battery shown in FIG. 57.

FIG. 59 is a top view of the battery shown in FIG. 57.

FIG. 60 is a rear view of the battery shown in FIG. 57.

FIG. 61 is a schematic diagram of the prior art battery shown in FIG. 57and the battery charger shown in FIG. 40.

FIG. 62 is a perspective view of a prior art battery charger.

FIG. 63 is a side view of the battery charger shown in FIG. 62.

FIG. 64 is another view of the battery charger shown in FIG. 62.

FIG. 65 is a schematic diagram of the prior art battery shown in FIG. 57and the prior art battery charger shown in FIG. 62.

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other constructions and of being practicedor of being carried out in various ways. Also, it is to be understoodthat the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having” and variations thereof herein ismeant to encompass the items listed thereafter and equivalents thereofas well as additional items. The terms “mounted,” “connected,” and“coupled” are used broadly and encompass both direct and indirectmounting, connecting and coupling. Further, “connected” and “coupled”are not restricted to physical or mechanical connections or couplingsand can include electrical connections and couplings, whether direct orindirect.

DETAILED DESCRIPTION

A battery pack or battery 50 is illustrated in FIGS. 1-3. The battery 50can be configured for transferring power to and receiving power from oneor more electrical devices, such as, for example, a power tool 55 (shownin FIGS. 4-5), a battery charger 60 (shown in FIG. 24) and the like. Asshown in the constructions illustrated in FIGS. 4 and 5, the battery 50can transfer power to various power tools, such as a circular saw 56 anda driver drill 58, for example. In some constructions and in someaspects, the battery 50 can supply a high discharge current toelectrical devices, such as, for example, a power tool 55, havinghigh-current discharge rates. For example, the battery 50 can power awide range of power tools 55 including a circular saw 56, a driver drill58, and the like, as shown in FIGS. 4 and 5.

In some constructions and in some aspects, the battery 50 can have anybattery chemistry such as, for example, lead-acid, Nickel-cadmium(“NiCd”), Nickel-Metal Hydride (“NiMH”), Lithium (“Li”), Lithium-ion(“Li-ion”), another Lithium-based chemistry or another rechargeable ornon-rechargeable battery chemistry. In the illustrated constructions,the battery 50 can have a battery chemistry of Li, Li-ion or anotherLi-based chemistry and can supply an average discharge current that isequal to or greater than approximately 20 A. For example, in theillustrated construction, the battery 50 can have a chemistry of LithiumCobalt (“Li—Co”), Lithium Manganese (“Li—Mn”) Spinel, or Li—Mn Nickel.

In some constructions and in some aspects, the battery 50 can also haveany nominal voltage. In some constructions, for example, the battery 50can have a nominal voltage of approximately 9.6 V. In otherconstructions, for example, the battery 50 can have a nominal voltage upto approximately 50 V. In the some constructions, for example, thebattery 50 can have a nominal voltage of approximately 21 V. In otherconstructions, for example, the battery 50 can have a nominal voltage ofapproximately 28 V.

The battery 50 also includes a housing 65 which can provide terminalsupports 70. The battery 50 can further include one or more batteryterminals (not shown in FIGS. 1-5) supported by the terminal supports 70and connectable to an electrical device, such as the power tool 55, thebattery charger 60, and the like.

In some constructions and in some aspects, the housing 65 cansubstantially enclose a supporting circuit electrically connected to oneor more battery terminals. In some constructions, the circuit mayinclude a microcontroller or microprocessor. In some constructions, thecircuit can communicate with the electrical devices, such as a powertool 55 (e.g., a circular saw 56, a driver drill 58, and the like), abattery charger 60, and the like, and can provide information to thedevices regarding one or more battery characteristics or conditions,such as, for example, the nominal voltage of the battery 50, thetemperature of the battery 50, the chemistry of the battery 50 andsimilar characteristics, as discussed below.

The battery 50 is schematically illustrated in FIGS. 6A-D, 7-10, 11A-Dand 12A-C and portions of the battery 50 are shown in FIGS. 13-16 and20A-B. As illustrated, the battery 50 can include one or more batterycells 80 each having a chemistry and a nominal voltage. Also, eachbattery cell 80 can include a positive end 90 and a negative end 95. Insome constructions such as, for example, the constructions illustratedin FIGS. 6A and C, the battery 50 can have a battery chemistry ofLi-ion, a nominal voltage of approximately 18 V or approximately 21 V(depending on the type of battery cell, for example), and can includefive battery cells 80 a, 80 b, 80 c, 80 d and 80 e. In otherconstructions, such as for example the constructions illustrated inFIGS. 6B and D, the battery 50 can have a battery chemistry of Li-ion, anominal voltage of approximately 24 V, approximately 25 V orapproximately 28 V (depending on the type of battery cell, for example)and can include seven battery cells 80 a, 80 b, 80 c, 80 d, 80 e, 80 fand 80 g. In further constructions, the battery 50 can have more orfewer battery cells 80 than shown and described. In an exemplaryconstruction, each battery cell 80 has a chemistry of Li-ion, and eachbattery cell 80 has substantially the same nominal voltage, such as, forexample, approximately 3.6 V, approximately 4 V or approximately 4.2 V.

In some constructions, two or more battery cells 80 can be arranged inseries with the positive end 90 of one battery cell 80 electricallyconnected to the negative end 95 of another battery cell 80, as shown inFIGS. 6A and C. The battery cells 80 can be electrically connected by aconductive link or strap 100. In other constructions, the battery cells80 can be arranged in another manner such as, for example, in parallelwith the positive ends 90 of the battery cells 80 a-e electricallyconnected to each other and the negative ends 95 of the battery cells 80a-e electrically connected to each other or in a combination of seriesand parallel. As shown in FIGS. 6B and D, the battery cells 80 can beindividually coupled to a circuit 130. In some constructions, thecircuit 130 can configure the battery cells 80 into various arrangementssuch as, for example, in a parallel arrangement, a serial arrangement(such as the series of battery cells 80 illustrated in FIGS. 6A and C),an individual arrangement (e.g., drawing current from or supplyingcurrent to a single battery cell 80), a partial parallel arrangement(e.g., arranging a few of the battery cells 80 into a serialarrangement), a partial serial arrangement (e.g., arranging a few of thebattery cells into a parallel arrangement), or a combination of theserial, partial serial, parallel, and partial parallel arrangements. Insome constructions, a circuit 130 included in the battery 50 canestablish the arrangements permanently via software (e.g., a programexecuted by a processor, such as microprocessor 140 discussed below) orhardware. In some constructions, the circuit 130 can modify thearrangements via software or hardware (e.g., one or more switches, logiccomponents, and the like)

The battery 50 can also include a terminal block 105 which may includethe one or more battery terminals supported by the terminal supports 70(shown in FIG. 1). In the illustrated construction, the terminal block105 can include a positive terminal 110, a negative terminal 115, and asense terminal 120. The positive terminal 110 can be electricallyconnected to the positive end 90 of a first battery cell 80 a, and thenegative terminal 115 can be electrically connected to the negative end95 of a second battery cell 80 e (or battery cell 80 g). In theillustrated constructions, the first battery cell 80 a is the first cellof the battery cells 80 to be serially linked, and the second batterycell 80 e or 80 g is the last cell of the battery cells 80 a-e or 80 a-gto be serially linked, respectively.

As mentioned previously, the battery 50 can include a circuit 130. Thecircuit 130 can be electrically connected to one or more battery cells80, and can be electrically connected to one or more battery terminalsof the terminal block 105. In some constructions, the circuit 130 caninclude components to enhance the performance of the battery 50. In someconstructions, the circuit 130 can include components to monitor batterycharacteristics, to provide voltage detection, to store batterycharacteristics, to display battery characteristics, to inform a user ofcertain battery characteristics, to suspend current within the battery50, to detect temperature of the battery 50, battery cells 80, and thelike, to transfer heat from and/or within the battery 50. In someconstructions and in some aspects, the circuit 130 includes a voltagedetection circuit, a boosting circuit, a state of charge indicator, andthe like, as discussed below. In some constructions, the circuit 130 canbe coupled to a print circuit board 145, discussed below. In otherconstructions, the circuit 130 can be coupled to a flexible circuit 145.In some constructions, the flexible circuit 145 can wrap around one ormore cells 80 or wrap around the interior of the housing 65.

In some constructions and in some aspects, the circuit 130 can alsoinclude a microprocessor 140. The microprocessor 140 can store batterycharacteristics or battery identification information, such as, forexample, battery chemistry, nominal voltage, and the like. In otherconstructions and in other aspects, the microprocessor 140 can storeadditional battery characteristics, such as, for example, batterytemperature, ambient temperature, number of times the battery 50 hasbeen charged, the number of times the battery has been discharged,various monitoring thresholds, various discharging thresholds, variouscharging thresholds, and the like, and can store information about themicroprocessor 140 itself and its operation, such as, for example,frequency and/or number of times battery characteristics have beencalculated, number of times the microprocessor 140 disabled the battery50, and the like. The microprocessor 140 can also control otherelectrical components of the circuit 130 included in the battery 50, asdiscussed below.

In the illustrated construction and in some aspects, the microprocessor140 can be electrically connected to a printed circuit board (“PCB”)145. In the illustrate construction, the PCB 145 can provide thenecessary electrical connections between the microprocessor 140 and theterminals 110, 115 and 120, the battery cells 80 a-g and otherelectrical components included in the battery 50, as discussed below. Inother constructions, the PCB 145 may include additional electricalcircuitry and/or components, such as, for example, additionalmicroprocessors, transistors, diodes, current-limiting components,capacitors, etc.

In some constructions and in some aspects, the circuit 130 also caninclude a temperature-sensing device, such as, for example, a thermistor150 or a thermostat (not shown). The temperature-sensing device cansense the temperature of one or more battery cells 80 a-g included inthe battery 50, can sense the temperature of battery 50 as a whole, orcan sense ambient temperature and the like. In some constructions, theresistance value of the thermistor 150 can be indicative of thetemperature of the one or more battery cells 80 a-g being sensed and canchange as the temperature of the one or more battery cells 80 a-gchanges. In some constructions, the microprocessor 140 can determine thetemperature of the one or more battery cells 80 a-g based on theresistance value of the thermistor 150. The microprocessor 140 can alsomonitor the change in temperature verses time by monitoring thethermistor 150 over time. The microprocessor 140 can also send thetemperature information to an electrical device, such as the power tool55 and/or the battery charger 60, and/or use the temperature informationto initiate certain functions or to control other components within thebattery 50, as discussed below. As shown in the illustratedconstruction, the thermistor 150 is mounted on the PCB 145.

In some constructions and in some aspects, the circuit 130 can alsoinclude a present state of charge indicator, such as, for example, afuel gauge 155 shown in the illustrated constructions. The fuel gauge155 can include a light-emitting diode (“LED”) display that indicatesthe present state of charge of the battery 50. In other constructions,the fuel gauge 155 can include a matrix display. As shown in FIGS. 1-3,the fuel gauge 155 can be located on an upper face 157 of the batteryhousing 65. In other constructions, the fuel gauge 155 can be locatedanywhere on the housing 65 such as, for example, on a lower face 158 ofthe housing 65, on one of the sides 159 of the housing 65, on the bottomface 161 of the housing, on the rear face 162 of the housing 65, on twoor more of the faces or sides of the housing 65, and the like.

In some constructions, the gauge 155 can be enabled via a push-buttonswitch 160 located on the housing 65 of the battery 50. In otherconstructions, the gauge can be activated automatically by a predefinedtime period as counted by a timer, by a predefined batterycharacteristic, and the like. In the illustrated construction, the gauge155 can be electrically connected to the microprocessor 140 via a ribboncable 165 and can include four LEDs 170 a, 170 b, 170 c and 170 dproviding the LED display.

In some constructions, the microprocessor 140 can determine the presentstate of charge of the battery 50 (i.e., how much charge is left in thebattery 50) when the push-button 160 is depressed and outputs the chargelevel to the fuel gauge 155. For example, if the present state of chargeof the battery 50 is approximately 100%, all of the LEDs 170 a, 170 b,170 c and 170 d will be turned on by the microprocessor 140. If thepresent state of charge of the battery 50 is approximately 50%, only twoof the LEDs, such as, for example, LEDs 170 a and 170 b, will be turnedon. If the present state of charge of the battery 50 is approximately25%, only one of the LEDs, such as, for example, LED 170 a, will beturned on.

In some constructions, the output can be displayed on the fuel gauge 155for approximately a predefined time period (i.e., a “displaying timeperiod”) after the push-button 160 is initially depressed. In someconstructions, the microprocessor 140 can disable the fuel gauge 155 oroutput a zero present state of charge output if the temperature of oneor more battery cells 80 a-g exceed a predetermined threshold. In someconstructions, the microprocessor 140 can disable the fuel gauge 155 oroutput a zero present state of charge output when an abnormal batterycharacteristic such as, for example, a high battery temperature, isdetected even if the battery 50 has a relatively high charge levelremaining. In some constructions, the microprocessor 140 can disable thefuel gauge 155 or output a zero present state of charge output if thepresent state of charge of the battery 50 or the present state of chargeof one or more cells 80 a-g fall below a predetermined threshold. Insome constructions, the microprocessor 140 can disable the fuel gauge155 or output a zero present state of charge output approximately aftera predefined time period (i.e., a “cut-off time period”) regardless ifthe push-button 160 remains depressed or not. In some constructions, thecut-off time period can be substantially equal to the displaying timeperiod, and, in other constructions, the cut-off time period can begreater than the displaying time period.

In some constructions, the microprocessor 140 does not enable the fuelgauge 155 when the push-button 160 is depressed during time periods whenthe battery 50 is active (e.g., during charging and/or discharging).Present battery state of charge information can be suppressed duringthese time periods to avoid erroneous state of charge readings. In theseconstructions, the microprocessor 140 may only provide present state ofcharge information in response to the depressed push-button 160 when thecurrent through the battery 50 (e.g., charging current, dischargingcurrent, parasitic current, etc.) is below a predefined threshold.

In some constructions, the microprocessor 140 can enable the fuel gauge155 whether or not the push-button 160 is depressed during time periodswhen the battery 50 is active (e.g., during charging and/ordischarging). In one construction for example, the fuel gauge 155 can beoperational during charging. In this construction, the microprocessor140 can automatically enable the fuel gauge 155 to display the currentstate of charge of the battery 50 continuously, periodically (e.g.,after certain predetermined time intervals or during periods of lowcurrent draw/supply), in response to certain battery characteristics(e.g., when the current state of charge reaches certain definedthresholds, such as, every 5% increase in state of charge), or inresponse to certain stages, modes, or changes in the charge cycle. Inother constructions, the microprocessor 140 may enable the fuel gauge155 in response to the depression of the push-button 160 when thebattery 50 is active.

In some constructions and in some aspects, the fuel gauge 155 can beenabled via a touch pad, a switch, or the like. In other constructions,the battery 50 can include another push-button or switch (not shown) forenabling and disabling an automatic displaying mode. In theseconstructions, a user can select whether to have the circuit 130 operatein an automatic displaying mode or operate in a manual displaying mode.The automatic displaying mode can include the fuel gauge 155 displayingthe current state of charge of the battery 50 without user activation.For example, in the automatic displaying mode, the fuel gauge 155 candisplay the current state of charge of the battery 50 periodically(e.g., after certain predetermined time intervals), in response tocertain battery characteristics (e.g., when the current state of chargereaches certain defined thresholds, such as, every 5% increase ordecrease in state of charge), or the like. The manual displaying modecan include the fuel gauge 155 displaying the current state of charge inresponse to user activation such as, for example, the depression of thepush-button 160. In some constructions, the push-button 160 can bedisabled when the circuit 130 is operating in the automatic displayingmode. In other constructions, the push-button 160 can still enable thefuel gauge 155 even when the circuit 130 is operating in the automaticdisplaying mode. In further constructions, the automatic displaying modecan be enabled and disabled via the push-button 160, a control signalfrom an electrical device such as, for example, a power tool 55 orbattery charger 60, or the like.

In some constructions, the circuit 130 can include a boosting circuit171. The boosting circuit 171 can providing additional power forcomponents included in the circuit 130 during periods of low batteryvoltage, as discussed below. For example, the microprocessor 140 mayneed a voltage source of approximately 3 V or approximately 5 V in orderto operate. If the present state of charge of the battery 50 falls belowabout 5 V or about 3 V, then the microprocessor 140 may not receiveenough power to operate and control the remainder of the componentsincluded in the circuit 130. In other constructions, the boostingcircuit 171 can “boost” a lower input voltage into a higher outputvoltage, as discussed below.

Various constructions of the boosting circuit 171 are illustrated inFIGS. 11A-F. In one construction such as, for example, the constructionshown in FIG. 11A, the boosting circuit 171 a can include a power sourceor power component such as, for example, another battery cell 172. Insome constructions, the battery cell 172 can be different in chemistry,nominal voltage and the like than the battery cells 80 connected inseries. For example, the battery cell 172 can be a 1.2 V cell of Li-ion.

In some constructions, the boosting circuit 171 a may only supply powerto the remainder of the circuit 130 (such as, for example, themicroprocessor 140) when the combined present state of charge of thebattery cells 80 drops below a threshold. In some constructions, theboosting circuit 171 a may only supply power to the remainder of thecircuit 130 when the temperature of the battery cells 80 drops below alow temperature threshold and when the combined present state of chargeof the battery cells 80 drops below a low voltage threshold. In otherconstructions, the boosting circuit 171 a may only supply power to theremainder of the circuit 130 during periods of operation in lowtemperature conditions (e.g., the pack temperature is below a lowtemperature threshold, or the ambient temperature is below a lowtemperature threshold). In these constructions, the boosting circuit 171a may only supply power in order to prevent the circuit 130 (e.g., themicroprocessor 140) from experiencing a “brown-out” condition (e.g., aninsufficient supply of voltage for a period of time). A brown-outcondition may be caused by battery voltage fluctuations which can bemore evident or pronounced during low operating temperatures (e.g.,either pack temperature or ambient temperature).

In another construction such as, for example, the constructionillustrated in FIG. 11B, the boosting circuit 171 b can include a boostmechanism 173 such as, for example, an inductive “flyback” typeconverter, a switched capacitor converter, and the like. Similar toboosting circuit 171 a, the boosting circuit 171 b may supply power tothe remainder of the circuit 130 in response to various batteryconditions.

In yet another construction such as, for example, the constructionillustrated in FIG. 11C, the boosting circuit 171 can be a capacitiveboosting circuit 171 c. As shown, the capacitive boosting circuit 171 ccan include a capacitor 174. During operation, the capacitor 174 can becharged either by the discharge circuit from the battery cells 80 or bya signal from the microprocessor 140 or additional circuitry. Similar toboosting circuit 171 a, the boosting circuit 171 c may supply power tothe remainder of the circuit 130 in response to various batteryconditions.

In a further construction such as, for example, the constructionillustrated in FIG. 11D, the boosting circuit 171 d can include atransistor or switch 175. In some constructions, the switch 175 can be apower field effect transistor (“FET”) 180, as discussed below. In anexemplary implementation, the switch 175 is a FET. In someconstructions, the boosting 171 d can operate by interrupting thedischarge current from a certain period of time to allow the presentstate of charge of the battery 50 to recover. For example, the batterycells 80 may experience large voltage fluctuations due to low celltemperature, low ambient temperature, high discharge current (e.g.,large load), and the like. By interrupting the discharge current for aperiod of time, the large fluctuations in state of charge may reduce,and the voltage of the battery cells 80 may rise. Activating anddeactivating the switch 175 may prevent the large fluctuations fromcreating a brown-out condition for the circuit 130. Similar to theboosting circuit 171 a, the boosting circuit 171 d may be activated inresponse to certain battery conditions such as, for example, lowtemperature, low battery state of charge, and the like. In someconstructions, the switch 175 can be used in combination with thecapacitor 174 of circuit 171 c to recharge the capacitor 174.

In some constructions, the switch 175 can be activated (e.g.,repetitively switched) at a set frequency or duty cycle. In otherconstructions, the switch 175 can be activated in a hysteretic manner.For example, the switch 175 may only be activated if the voltage of thebattery 50 reaches or drops below a first threshold. The switch 175 mayremain open (e.g., interrupting the current flow) until the presentstate of charge of the battery 50 recovers to or exceeds a secondthreshold, typically greater than the first threshold. In someconstructions, the second threshold can equal the first threshold. Insome constructions, the more the battery state of charge is depleted,the time period that the state of charge takes to recover or reach thesecond threshold can be longer. In these instances, the circuit 130 canalso include a timer (not shown). When a first time kept by the timerexpires and the state of charge has not recovered to the secondthreshold, then the circuit 130 can infer that the battery 50 is fullydischarged, and can continue to have the switch 175 remain open toprevent the battery 50 from entering an over-discharged state.

In a further construction such as, for example, the constructionsillustrated in FIGS. 11E and 11F, the boosting circuit 171 can be acapacitive charge pump boost circuit such as the boosting circuits 171 eand 171 f. In these constructions, the boosting circuits 171 e and 171 fcan “boost” one or more lower voltage signals into a higher outputvoltage signal. As shown in FIG. 11 e, the boosting circuit 171 e caninclude one or more inputs 176 a-f for receiving AC signals, controlssignal, and the like, and one or more low voltage inputs 179 forreceiving one or more low voltage signals. The signals (e.g., the ACsignals and/or the control signals) can be used to increase the lowvoltage signals and the charge stored on (or the voltage across) acapacitor 178, and generate a higher voltage output signal at output177. Similar to the boosting circuit 171 e, boosting circuit 171 f canalso include one or more inputs 176 a-d for receiving low voltage ACpower signals, control signals, and the like, and one or more lowvoltage inputs 179 for receiving one or more low voltage signals. In anexemplary implementation, the boosting circuit 171 e can boost anapproximately 3 V input signal to an approximately 10 V output signal,and the boosting circuit 171 f can boost an approximately 3 V inputsignal to an approximately 5 V output signal.

In some constructions, the boosting circuits 171 e and 171 f can providehigher voltage signals to components within the circuit 130 at any timeand during any battery condition. For example, the boosting circuit 171e can provide an output signal to power a power FET or switch, asdiscussed below, and the boosting circuit 171 f can provide an outputsignal to power one or more transistors, as discussed below.

In some constructions and in some aspects, the circuit 130 can include asemiconducting switch 180 that interrupts the discharging current whenthe circuit 130 (e.g., the microprocessor 140) determines or senses acondition above or below a predetermined threshold (i.e., an “abnormalbattery condition”). In some constructions, an abnormal batterycondition can include, for example, high or low battery celltemperature, high or low battery state of charge, high or low batterycell state of charge, high or low discharge current, high or low chargecurrent, and the like. In the illustrated constructions, the switch 180includes a power FET or a metal-oxide semiconductor FET (“MOSFET”). Inother constructions, the circuit 130 can include two switches 180. Inthese constructions, the switches 180 can be arranged in parallel.Parallel switches 180 can be included in battery packs supplying a highaverage discharge current (such as, for example, the battery 50supplying power to a circular saw 56, a driver drill 58, and the like).

In some constructions, the circuit 130 can further include a switchcontrol circuit 182 to control the state of the switch 180 (or switches180 if applicable). In some constructions, the switch control circuit182 can include a transistor 185 such as, for example, a npn-bipolarjunction transistor or a field-effect transistor (“FET”). In theseconstructions, the circuit 130 (e.g., the microprocessor 140) cancontrol the switch 180 by changing the state of the transistor 185. Asshown in FIGS. 7-9, the source 190 of the FET 180 can be electricallyconnected to the negative end 95 of the battery cell 80 a-e, and thedrain 195 of the FET 180 can be electrically connected to the negativeterminal 115. The switch 180 can be mounted to a second PCB 200 (shownin FIG. 7). In some constructions and in some aspects, such as, forexample, the constructions illustrated in FIGS. 14A-E, the switch 180can be mounted on the PCB 145. In other constructions, the switch 180can be mounted in another suitable position or location.

In an exemplary implementation, current will flow through the switch 180from the drain 195 to the source 190 during discharging, and currentwill flow through the switch 180 from the source 190 to the drain 195during charging. In the event an abnormal battery condition is detectedby the circuit 130 (e.g., the microprocessor 140), the microprocessor140, for example, can turn on the transistor 185, that is, bias thetransistor 185 into a conducting state. When the transistor 185 is in aconducting state, there is not enough voltage across the gate 205 andthe source 190 of the FET 180 for the switch 180 to be in a conductingstate. Thus, the FET 180 becomes non-conducting, and current flow isinterrupted.

In some constructions, once the switch 180 becomes non-conducting, theswitch 180 may not reset even if the abnormal condition is no longerdetected. In some constructions, the circuit 130 (e.g., themicroprocessor 140) may reset the switch 180 only if an electricaldevice, such as, for example, a battery charger 60, instructs themicroprocessor 140 to do so. In some constructions, the microprocessor140 may reset the switch 180 after a predefined time period. In someconstructions, if the microprocessor 140 detects an abnormal batterycondition during discharge, the microprocessor 140 may not change thestate of the switch 180 to non-conducting until the microprocessor 140also detects a discharge current below a predetermined threshold (i.e.,a low discharge current).

In some constructions, the switch 180 can be configured to onlyinterrupt current flow when the battery 50 is discharging. That is, thebattery 50 can be charged even when the switch 180 is in thenon-conducting state. As shown in FIGS. 4 and 5, the switch 180 caninclude a body diode 210, which, in some constructions, is integral witha MOSFET and other transistors. In other constructions, the diode 210can be electrically connected in parallel with the switch 180.

In another exemplary implementation, when the battery 50 is beingdischarged (i.e., represented in FIG. 5 as a switch 215 being in a firstposition 220 to allow current to flow through a load 225, such as, forexample, a power tool 55), current flows through the battery 50 indirection 230, that is, through the drain 190 of the FET 180 to thesource 190 of the FET 180. When the battery 50 is being charged (i.e.,represented in FIG. 5 as the switch 215 being positioned in a secondposition 235 to allow current to flow from an electric device, such as,for example, a battery charger 60), current flows through the battery 50in direction 240, that is, through the source 190 of the FET 180 to thedrain 195 of the FET 180.

In this implementation, current flow in the direction 230 may beinterrupted when the switch 180 is in the non-conducting state.Therefore, the battery 50 no longer supplies a discharge current to theload 225. In some constructions, the circuit 130 including, for example,the microprocessor 140 or additional circuitry 250 (which may or may notinclude the microprocessor 140), may change the state of the switch 180from non-conducting to conducting when the microprocessor 140 receivesan instruction or command to do so. In some constructions, themicroprocessor 140 and/or additional circuitry 250 may not receive acommand or an instruction and, therefore, may not change the state ofthe switch 180 from non-conducting to conducting. For example, thebattery 50 may become deeply discharged that the battery 50 does nothave enough power in the battery cells 80 to power the circuit 130. Ifthe battery 50 does not have enough power to power the circuit 130,communication (as performed by the circuit 130) between the battery 50and an electrical device (e.g., battery charger 60) may not be able totake place and then the electrical device may not be able to send acontrol signal to the battery 50 to re-set the switch 180. In theseinstances, the body diode 210 included in the switch 180 may conductcurrent in the direction 240 (i.e., a charging current) supplied by anelectrical device such as, for example, the battery charger 60. This canallow the battery 50 to be charged even if the switch 180 is notconducting, or at least receive enough charge to power the circuit 130,re-set the switch 180, and commence communication or charging.

In some constructions and in some aspects, the circuit 130 (e.g.,microprocessor 140) can monitor battery cell voltage for an abnormalcondition (e.g., low battery cell voltage) and can activate the switch180 to interrupt the discharge current if an abnormal condition isdetected. In some constructions, battery cell damage can occur if thecell voltage drops to or below a certain voltage, such as, for example,a cell “reversal” voltage. In some constructions, cell reversal occursat approximately 0 V. In some constructions, the microprocessor 140 orthe circuit 130 can establish a cell reversal threshold as apreventative precaution. In some constructions, the cell reversalthreshold can be set at the cell reversal voltage. In otherconstructions, the cell reversal threshold can be set higher than thecell reversal voltage. For example, the cell reversal threshold can beset for approximately 1 V.

In some instances, the battery 20 can experience a voltage “depression”(e.g., large temporary drop in voltage) during the start of discharge.The voltage depression can typically be temporary and most evident atlow battery temperatures. In some constructions, a voltage depressioncan drop to or below the cell reversal threshold.

In some constructions and in some aspects, the circuit 130, such as themicroprocessor 140, can include variable response times for respondingor reacting to monitored battery characteristics. In some constructions,the variable response time can include multiple monitoring modes for thecircuit 130. That is, the circuit 130 (e.g., the microprocessor 140) canoperate in multiple modes when detecting and/or monitoring batterycharacteristics such as, for example, cell state of charge, batterystate of charge, and other similar battery characteristics. For example,the microprocessor 140 can include a first mode with a first samplingrate and a second mode with a second sampling rate. In someconstructions, the first sampling rate can be set and can differ fromthe second sampling rate, which can also be set. In other constructions,the first sampling rate can be dependent on a first parameter, which mayinclude, for example, one or more battery characteristics, one or morecontrol signals from an electrical device (e.g., the power tool 55 orthe battery charger 60), or the like, and may vary according to thatfirst parameter. Similarly, the second sampling rate can also bedependent on the first parameter or can be dependent on a secondparameter (similar to the first parameter, for example), and may varyaccording to that second parameter. In other constructions, themicroprocessor 140 can include additional sampling rates and additionalmodes, as will be discussed below.

In some constructions, for example, the microprocessor 140 can operatein a first mode or “slow” mode. In these constructions, operation in theslow mode can reduce activation of the switch 180 due to voltagedepressions by prolonging the response time. In some constructions, themicroprocessor 140 may operate in the slow mode when the load on thebattery 20 is not high enough to require a fast response time (e.g., thecurrent draw is relatively low). In some constructions, themicroprocessor 140 may operate in the slow mode until the presentbattery state of charge remaining drops below a predefined threshold,such as, for example, approximately 10% state of charge remaining.

In an exemplary implementation, the microprocessor 140 can sample thecell voltages at a slow rate, such as, for example, once per second,when operating in the slow mode. Since the microprocessor 140 issampling at a slow rate, the microprocessor 140 experiences a slowerresponse time. In some constructions, the slow mode may be adequate formost monitoring conditions and can reduce the quiescent current drawn bythe circuit 130 (e.g., the microprocessor 140 and additional circuitry).In some constructions, the microprocessor 140 can operate in the slowmode as long as the cell voltages are above a predefined threshold or“mode switch” threshold, such as, for example, 3.73 V.

In some constructions, the microprocessor 140 can operate in a secondmode or “fast” mode. In these constructions, operation in the fast modecan quicken the response time for detecting an abnormal condition. Insome constructions, the microprocessor 140 can operate in the fast modewhen the one or more cell voltages drop to the predefined threshold or“mode switch” threshold, such as, for example, 3.73 V. In someconstructions, the microprocessor 140 can operate in the fast mode whenthe present battery state of charge remaining drops to a predefinedthreshold, such as, for example, approximately 10% state of chargeremaining.

In another exemplary implementation, the microprocessor 140 samples thecell voltages at a fast rate, such as, for example, 100 samples persecond when operating in the fast mode. In some constructions, the cellvoltages sampled by the microprocessor 140 may be averaged over acertain number of samples before activation of the switch 180 occurs. Insome constructions, for example, the switch 180 may not be activated bythe microprocessor 140 unless the average of thirty samples is equal toor less than the cell reversal threshold. Averaging the samples can havean effect of digitally “filtering” the voltage information that is readby the microprocessor 140 and can provide some delay for themicroprocessor 140 to ignore the “inrush” current and/or voltagedepressions. Averaging the samples can also have an effect of filteringthe voltage information from electrical noise due to external speedcontrol circuits. In some constructions, the number of samples foraveraging can vary depending on the operating mode of the microprocessor140, the type of battery characteristic being monitored, and the like.

In some constructions, the microprocessor 140 may also activate theswitch 180 when operating in the fast mode if the cell voltages dropbelow a predefined threshold, such as a cut-off threshold, for a certainamount of time such as, for example, several seconds. In someconstructions, the cut-off threshold can be greater than the cellreversal threshold. For example, the cut-off threshold may beapproximately 2 V, and the cell reversal threshold may be approximately1 V. In cases where voltage drops below 1 V, response time my be muchfaster (on the order of 300 ms). The variable response times can reducethe amount of nuisance shut-downs while still protecting the cellsadequately.

In some constructions, the voltage thresholds (the cut-off threshold andthe cell reversal threshold) can be adjusted up or down by themicroprocessor 140 in accordance with the battery temperature. This canallow for the optimization based on battery temperature characteristics.

In a further exemplary implementation, the microprocessor 140 canvarying the response times by varying the number of samples to beaveraged. For example, the microprocessor 140 can sample a batterycharacteristic such as, for example, battery temperature. According to afirst mode, the microprocessor 140 can have a “slow” response time byaveraging the battery temperature measurements over 50 samples.According to a second mode, the microprocessor 140 can have a “fast”response time by averaging the battery temperature measurements over 30samples. In some constructions, the measurements can be sampled at thesame rate. In other constructions, the measurements can be sampled atdifferent rates. For example, the first mode can sample the measurementsat a rate of approximately 1 sample per second, and the second mode cansample the measurements at a rate of approximately 10 samples persecond.

In some constructions, the microprocessor 140 can control and limit thecurrent draw without the need for current-sensing devices, because themicroprocessor 140 is capable of sensing a high discharge current bymonitoring cell voltages. For example, when a high current load causesthe cell voltages to drop to a low level, such as, for example, thecut-off threshold and/or the cell reversal threshold, the microprocessor140 may activate the switch 180 and disable the battery 20. Themicroprocessor 140 can indirectly limit the current draw by monitoringthe cell voltages and disable the battery 20 when the cell voltages dropto certain levels (e.g., the cut-off threshold and/or the cell reversalthreshold).

In some constructions and in some aspects, the circuit 130 (e.g., insome constructions, the microprocessor 140) can monitor batteryconditions (e.g., battery cell voltage/present state of charge, batterycell temperature, battery pack voltage/present state of charge, batterypack temperature, etc.) periodically to reduce the parasitic currentdraw from the battery 50. In these constructions, the microprocessor 140can operate in a “sleep” mode for a first predefined time period (i.e.,a “sleep time period”). During the sleep mode, the microprocessor 140may draw a low quiescent current from the battery 50. After the sleeptime period expires, the microprocessor 140 can “wake up” or, in otherwords, can operate in an active mode for a second predefined time period(i.e., an “active time period”). During the active mode, themicroprocessor 140 can monitor one or more battery conditions.

In some constructions, the sleep time period can be greater than theactive time period. In some constructions, the ratio of the active timeperiod to the sleep time period can be low such that the averageparasitic current draw is low. In some constructions, the ratio can beadjusted (e.g., increased) during time periods of known batteryactivity, such as, for example, when the microprocessor 140 senses adischarge current or a charge current approximately equal to apredetermined threshold. In some constructions, when the microprocessor140 detects certain voltage and/or temperature characteristics, thesleep time period can be decreased and/or the active time period can beincreased.

In some constructions and in some aspects, the circuit 130 can include avoltage detection circuit 259. In some constructions, the voltagedetection circuit 259 can include a plurality of resistors 260 formingresistor divider networks. As shown in the illustrated construction, theplurality of resistors 260 can include resistors 260 a-d. The pluralityof resistors 260 can be electrically connected to one or more batterycells 80 a-g and to a plurality of transistors 265. In the illustratedconstruction, the plurality of transistors 265 can include transistors265 a-d or 265 a-f. In some constructions, the number of resistorsincluded in the plurality of resistors 260 can equal the number oftransistors included in the plurality of transistors 265.

In some constructions, voltage characteristics of the battery 50 and/orof the battery cells 80 can be read by the microprocessor 140 throughthe plurality of resistors 260 when the microprocessor 140 is in theactive mode. In some constructions, the microprocessor 140 can initiatea voltage-read event by turning off transistor(s) 270 (i.e., transistor270 becomes non-conducting). When the transistor(s) 270 isnon-conducting, the transistors 265 a-d become conducting and voltagemeasurements regarding the battery 50 and/or battery cells 80 can bemade by the microprocessor 140. Including the plurality of transistors265 in the battery 50 can reduce the parasitic current draw from thebattery 50, because the transistors 265 are only conductingperiodically.

In some constructions and in some aspects, the microprocessor 140communicates battery pack characteristics and/or conditions toelectrical devices, such as, for example, a power tool 55 and/or abattery charger 60, when the battery 50 and the electrical device areelectrically connected. In some constructions, the microprocessor 140digitally communicates to the electrical device in a serial manner. Thesense terminal 120 of the battery 50 provides a serial communicationlink between the microprocessor 140 and the electrical device. Theinformation regarding the battery 50 that can be exchanged between themicroprocessor 140 and the electrical device includes, but is notlimited to, battery pack chemistry, battery pack nominal voltage,battery pack temperature, battery pack present state of charge, batterycell(s) nominal voltage, battery cell(s) temperature, battery cell(s)present state of charge, calibration techniques/information, charginginstructions, number of charge cycles, estimated remaining lifeexpectancy, discharging information, etc.

In some constructions, an electrical device, such as, for example, abattery charger 60, can calibrate the microprocessor 140 when electricalconnection is established. In some constructions, the measuringcircuitry included in the battery charger 60 will be more precise thanthe circuitry included in the battery 50. Therefore, the battery charger60 calibrates the microprocessor 140 and/or the circuit 130 included inthe battery 50 to improve battery measurements made by themicroprocessor 140 and/or by the circuit 130.

In some constructions, the circuit 130 can also include a voltageregulator 273. The voltage regulator 273 can supply an appropriatevoltage to the microprocessor 140, the LEDs 170 a-d of the fuel gauge155 and any other additional electrical component that requires aconstant voltage input. In the illustrated construction, the voltageregulator 273 can output approximately 5 V.

In some constructions and in some aspects, the battery 50 may include aheat sink 275. The heat sink 275 can be in thermal communication withthe power FET or switch 180. The heat sink 275 can serve to remove heatgenerated by the switch 180 away from the switch 180.

In some constructions and in some aspects, the battery 50 may alsoinclude a heat pipe (not shown) or a fan (not shown) to increase theamount of heat being transferred from the heat sink 275. Such a heatpipe can be in thermal communication with the heat sink 275 in order toremove heat collected by the heat sink 275. Such a fan or blower can bein a position to create a flow of cooling air to pass over the heat sink275. Vents (not shown) can be positioned in the housing 65 of thebattery 50 to allow cool air to enter the battery pack 50 and the heatedair to leave the battery pack 50. In some constructions, the heat pipeand/or fan can be positioned to collect and/or remove heat generated bythe battery cells 80 a-e in addition to or as a substitute for the heatgenerated by the heat sink 275.

In some constructions and in some aspects, the battery 50 can alsoinclude a phase change material 300 (see FIGS. 20-22). In suchconstructions, the phase change material 300 can be positioned to absorband/or to remove heat generated by the battery cells 80 a-g andconductive links 100 (not shown in FIGS. 20-22). As the phase changematerial 300 undergoes phase transformation (e.g., from solid to liquid,from liquid to gas, from liquid to solid, from gas to liquid, etc.) at aphase change temperature, a large amount of energy is absorbed orreleased (i.e., latent heat of fusion, latent heat of vaporization,etc.). During such a phase transformation, the phase change material 300can have a relatively constant temperature.

In an exemplary implementation, the temperature of the battery cells 80may increase as a load is applied to the battery cells 80. In someconstructions, as illustrated in FIG. 20, the phase change material 300can surround each of the battery cells 80. In such constructions, heatgenerated by the battery cells 80 may be first conducted to an exteriorsurface 305 of the battery cells 80, and then to the surrounding phasechange material 300. As the phase change material 300 continues toabsorb heat from the battery cells 80 and conductive links 100, thetemperature of the phase change material 300 can increase. As thetemperature of the phase change material 300 reaches the phase changetemperature, the phase change material 300 can begin to undergo a phasetransformation from a first phase to a second phase, while thetemperature of the phase change material 300 remains relatively constantand approximately equal to the phase change temperature. In someconstructions, the phase change material 300 may continue to undergophase transformation until the phase change material 300 has completelytransformed into the second phase and/or the load has been removed fromthe battery cells 80 (i.e., the battery cells 80 are no longergenerating heat).

In some constructions and in some aspects, the phase change material 300can have a phase change temperature greater than an expected ambienttemperature and less than a maximum allowable battery cell temperature.In some constructions and in some aspects, the phase change material 300can have a phase change temperature between −34° C. and 116° C. In someconstructions and in some aspects, the phase change material 300 canhave a phase change temperature in between 40° C. and 80° C. In someconstructions and in some aspects, the phase change material 300 canhave a phase change temperature between 50° C. and 65° C.

The phase change material 300 can be any suitable phase change material,can have a high latent heat per unit mass, can be thermally cyclable,inert, non-corrosive, non-contaminating, and can comprise paraffin waxes(such as those available from Rubitherm® headquartered in Hamburg,Germany), eutectic mixtures of salts (such as those available fromClimator based in Skovde, Sweden), halogenated hydrocarbons and mixturesthereof, salt hydrate solutions, polyethylene glycol, stearic acid, andcombinations thereof.

An alternate construction of a battery 50A is illustrated in FIGS. 21and 22. Common elements have the same reference number “A”.

In the illustrated construction, the battery 50A can further include aheat sink 275A to spread heat from the battery cell 80A over a greaterarea of the phase change material 300A. The heat sink 275A may also beemployed to provide additional heat storage capacity to absorb and/orremove heat generated by the battery cells 80A.

In some constructions, the heat sink 275A may comprise one element (notshown) that wraps each and all of the battery cells 80 a-e. In otherconstructions, the heat sink 275A may comprise multiple pieces such thateach battery cell 80A is substantially wrapped by a heat sink 275A, asshown in FIGS. 21 and 22. In still other constructions, as shown in FIG.21, the heat sink 275A may include an inner cylindrical portion 320adjacent the exterior surface 305A of the battery cell 80A, an outercylindrical portion 325 disposed a radial distance from the innercylindrical portion 320 and radial ribs 330 spaced a circumferentialdistance from one another that connect the inner cylindrical portion 320and the outer cylindrical portion 325 and define a space 335therebetween. The space 335 may be filled with phase change material300A. A similar configuration as that shown in FIG. 21 may also beemployed to encapsulate multiple battery cells (not shown). In yet otherconstructions, the heat sink 275A may comprise radial ribs 330, asdescribed above, without employing either or both of the innercylindrical portion 320 and the outer cylindrical portion 325.

In another alternate construction, as shown in FIG. 22, the heat sink275B can include an inner cylinder portion 320B and radial ribs 330B asdescribed above, and the phase change material 300B may be offset fromthe battery cell 80B and the heat sink 275B. It should be understoodthat other heat sink and phase change material configurations arepossible. The heat sink 275 may be formed of a metal (e.g., aluminum), apolymer (e.g., nylon), and/or any other material with high thermalconductivity and specific heat.

In some constructions and in some aspects, the battery 50 can includecushion members or “bumpers” 340. As shown in FIGS. 20A and B, theinterior face 345 of the battery housing 65 can include one or morecushion members 340. In some constructions, the cushion members 340 canbe integral with the housing 65. In other constructions, the cushionmembers 340 can be attached or secured to the interior face 345 of thehousing 65. In further constructions, the cushion member 340 can beconnected to one or more battery cells 80 or to an endcap 350 (partiallyshown in FIG. 16) surrounding one of the ends of the battery cells 80.In some constructions, the cushion members 345 can absorb energy duringimpact and protect the battery cells 80 during impact by limiting theamount of energy transferred to the cells 80. The cushion members 345can include any thermoplastic rubber such as, for example, polypropyleneRPT 100 FRHI (e.g., flame retardant-high impact).

As illustrated in FIGS. 21A-C, 22 and 23, the battery 50 can beconfigured to connect with an electrical device, such as the power tool55. The power tool 55 includes a housing 400. The housing can provide aconnection portion 405 to which the battery 50 can be connected. Theconnecting portion 405 can include one or more electrical deviceterminals (shown schematically in FIG. 22) to electrically connect thebattery 50 to the power tool 55. The terminals included in the powertool 55 are configured to mate with the terminals 110, 115 and/or 120included in the battery 50 and to receive power and/or information fromthe battery 50.

In some constructions, such as the constructions shown schematically inFIGS. 21A-C, the power tool 55 can include a microcontroller ormicroprocessor 420 to communicate with the battery 50, receiveinformation from the battery 50, control operation of the power tool 55,and/or control the discharging process of the battery 50. In theillustrated construction, the power tool 55 can include a positiveterminal 430 to connect to the positive terminal 110 of the battery 50,a negative terminal 435 to connect to the negative terminal 115 of thebattery 50 and a sense terminal 440 to connect to the sense terminal 120of the battery 50. The microprocessor 420 can be electrically connectedto each of the terminals 430, 435 and 440.

The microprocessor 420 can communicate with the battery 50 or receiveinformation from the battery 50 through the sense terminal 440regardless whether the battery 50 includes a microprocessor, such asmicroprocessor 140, or not. In constructions in which the battery 50includes a microprocessor, such as microprocessor 140, two-waycommunication can occur across the sense terminals 120 and 440. Themicroprocessors 140 and 420 can exchange information back and forth,such as battery characteristics, power tool operating time and powertool requirements (e.g., current and/or voltage ratings).

In constructions in which the battery 50 does not include amicroprocessor, the microprocessor 420 periodically measures or detectsone or more elements or components within the battery 50 to determinebattery characteristics and/or battery operating information, such as,for example, battery chemistry, nominal voltage, present battery stateof charge, cell voltages, temperature, etc. The microprocessor 420 cancontrol the operation of the power tool 55 based on these and otherbattery characteristics and operating information.

For example, in some constructions, the microprocessor 420 can beprogrammed to detect the battery temperature and disable the power tool55 if the battery temperature is above a threshold temperature. In thisexample, the microprocessor 420 periodically detects the resistance of athermistor 150 located in the battery 50 and determines the temperatureof the pack 50 during tool operation (i.e., when a motor 450 within thetool 55 is running). The microprocessor 420 then determines if thetemperature of the battery 50 is within an appropriate operating range.This can be accomplished by storing one or more temperature rangeswithin the microprocessor 420, allowing the microprocessor 420 tocompare the detected temperature of the battery 50 to the one or moreranges. If the temperature of the battery 50 is not within theappropriate operating range, the microprocessor 420 interrupts thecurrent flow from the battery 50 and/or shuts down the motor 450. Insome constructions, the microprocessor 420 continues to disable themotor 450 and/or interrupt the current flow from the battery 50 untilthe temperature of the battery 50 falls within the appropriate operatingrange. In some constructions in which the microprocessor 420 determinesthat the temperature of the battery 50 is not within an appropriateoperating range, the microprocessor 420 will not disable the motor 450until the microprocessor 420 detects a low discharge current beingsupplied to the motor 450 by the battery 50. In some constructions, themotor 450 is re-enabled (i.e., power tool 55 is operable) when themicroprocessor 420 detects that the battery 50 is removed from the powertool 55.

In some constructions and in some aspects, the power tool 55 can alsoinclude a fan or blower 470 to force cooling air through the tool 55 andbattery pack 50, as shown in FIG. 21B. The battery cells 80 a, heatsinks 275, heat pipes (not shown) and/or power FET or switch 180, ifincluded in the battery 50, can then be cooled by the passing air. Insuch a construction, the battery 50 and the power tool 55 include one ormore vents to allow cooling air in and to allow heated air out. Thepower tool 55 includes one or more inlet vents 475 which, in theillustrated construction, are positioned substantially on top of thepower tool housing 400. The power tool 55 also includes one or moreoutlet vents 480 which are positioned substantially on the bottom of theconnecting portion 405 of the power tool 55. The outlet vents 480included in the power tool 55 are also positioned such that the inletvents (not shown) of the battery 50 are substantially beneath the outletvents 480. In the illustrated construction, a motor 485 included in thepower tool 55 powers the fan 470. In some constructions, amicroprocessor 490 included in the power tool 55 controls the operationof the fan 470. The microprocessor 490 can activate the fan 470 duringpredetermined time intervals and/or if a high battery temperature isdetected.

As sown in FIG. 21C, the circuit 130 included in the battery 50 cancommunicate state of charge information to the microcontroller 420included in the power tool 55. In this construction, the microcontroller420 in the power tool 55 can display the battery state of chargeinformation on a fuel gauge 115 a included on or in the housing of thetool 55. In this construction, the fuel gauge 155 a can be similar tothe fuel gauge 155 included in the battery 50 and can be operated in asimilar fashion (e.g., in an automatic displaying mode, in a manualdisplaying mode, and the like). In some constructions, the fuel gauge155 a can include a push-button 160 and can include more or fewer LEDs(e.g., LEDS 170 a-d) than shown and described.

As shown in FIG. 23, the circuit 130 included in the battery 50 can alsobe used to control operation of an electrical device, such as a powertool 55. In the construction shown, the power tool 55 include a motor450, a trigger switch 491 activated by a user, a speed control circuit492, an electric clutch 493, and a brake 494. The tool 55 also includesa positive terminal 900 to connect to the positive terminal 105 of thebattery 50, a negative terminal 901 to connect to the negative terminal110 of the battery 50, and two sense terminals 902 a and 902 b toconnect to two sense terminals 120 a and 120 b of the battery 50,respectfully. In other constructions, the power tool 55 and battery 50can have more or fewer terminals than shown and described.

In this construction, the circuit 130 can provide tool speed control aswell as monitor battery pack parameters or characteristics. The powerMOSFET or switch 180 can control the switching function of the speedcontrol circuit of the tool 55. In this construction, the power MOSFETused for the speed control circuit 492 can be included in the battery 50rather than the power tool 55.

As shown in FIG. 24, the battery 50 is also configured to connect withan electrical device, such as the battery charger 60. The batterycharger 60 includes a housing 500. The housing 500 provides a connectionportion 505 to which the battery 50 is connected. The connecting portion505 includes one or more electrical device terminals (not shown) toelectrically connect the battery 50 to the battery charger 60. Theterminals included in the battery charger 60 are configured to mate withthe terminals included in the battery 50 and to transfer and receivepower and information from the battery 50.

In some constructions and in some aspects, the battery charger 60 alsoincludes a microprocessor or microcontroller 510. The microcontroller510 controls the transfer of power between the battery 50 and thebattery charger 60. In some constructions, the microcontroller 510controls the transfer of information between the battery 50 and thebattery charger 60. In some constructions, the microcontroller 510identifies and/or determines one or more characteristics or conditionsof the battery 50 based on signals received from the battery 50. Also,the microcontroller 510 can control operation of the charger 60 based onidentification characteristics of the battery 50.

In some constructions and in some aspects, the battery charger 60 basesthe charging scheme or method for charging the battery 50 on thetemperature of the battery 50. In one construction, the battery charger60 supplies a charging current to the battery 50 while periodicallydetecting or monitoring the temperature of the battery 50. If thebattery 50 does not include a microprocessor, the battery charger 60periodically measures the resistance of a thermistor, such as thermistor150, after predefined periods of time. If the battery 50 includes amicroprocessor, such as microprocessor 140, then the battery charger 60either: 1) interrogates the microprocessor 140 periodically to determinethe battery temperature and/or if the battery temperature is outside anappropriate operating range(s); or 2) waits to receive a signal from themicroprocessor 140 indicating that the battery temperature is not withinan appropriate operating range.

In some constructions, once the battery temperature exceeds a predefinedthreshold or does not fall within an appropriate operating range, thebattery charger 60 interrupts the charging current. The battery charger60 continues to periodically detect or monitor the battery temperatureor waits to receive a signal from the microprocessor 140 indicating thatthe battery temperature is within an appropriate operating range. Whenthe battery temperature is within an appropriate operating range, thebattery charger 60 may resume the charging current supplied to thebattery 50. The battery charger 60 continues to monitor the batterytemperature and continues to interrupt and resume the charging currentbased on the detected battery temperature. In some constructions, thebattery charger 60 terminates charging after a predefined time period orwhen the present battery state of charge reaches a predefined threshold.

In some constructions and in some aspects, the battery 50 and/or theelectrical devices, such as the power tool 55 and battery charger 60,are capable of detecting imbalanced battery cells within the battery 50.In some constructions, rather than monitoring each battery cell 80 a-eindividually, a microprocessor, such as, for example, the microprocessor140, 420, 490 and/or 510 (the “monitoring microprocessor”), monitorsonly two groups of battery cells 80 and determines cell imbalance usinga ratio of voltages of the two cell groups.

For example, a battery 600 is partially shown in FIG. 25. In someconstructions, the battery 600 is similar to battery 50 and includes amicroprocessor 140. In other constructions, the battery 600 does notinclude a microprocessor. In the illustrated construction, the battery600 includes five battery cells 605 a, 605 b, 605 c, 605 d and 605 e,each having substantially the same nominal voltage, such as, forexample, approximately 4 V.

The battery cells 605 a-e are arranged into two groups, group 610 andgroup 615. Group 610 includes battery cells 605 a and 605 b, and group615 includes battery cells 605 c, 605 d and 605 e.

The battery 600 also includes a lead or tap 620 which provides a voltageV₆₁₅ across group 615 (i.e., the total voltage of battery cells 605 c,605 d and 605 e). When the battery cells 605 a-e are approximately fullycharged, the voltage V₆₁₅ of group 615 equals approximately 12 V. Thevoltage V_(T) is the voltage across all of the battery cells 605 a-e.When the battery cells 605 a-e are substantially fully charged, thevoltage V_(T) equals approximately 20 V.

The monitoring microprocessor is programmed to monitor voltages V₆₁₅ andV_(T). In some constructions, the monitoring microprocessor monitors thevoltages V₆₁₅ and V_(T) either continuously or periodically andcalculates a ratio R between the measured voltages V₆₁₅ and V_(T). Theratio R is determined by the equation:R=V ₆₁₅ /V _(T)

When the cells 605 a-e are substantially balanced, the ratio R equalsapproximately 0.6. If one or more cells from the first group 610 areimbalanced (i.e., has a present cell state of charge or cell voltagelower than the other cells) during charging or discharging, the ratio Rwill be higher than 0.6. If one or more cells from the second group 615are imbalanced during charging or discharging, the ratio R will be lowerthan 0.6. If two cells, one from the first group 610 and one from thesecond group 615 (e.g., cell 605 a and cell 605 e) are imbalanced duringcharging or discharging, the ratio R will be higher than 0.6. In otherwords, if an imbalanced cell occurs, the ratio R will deviate plus orminus from the balanced ratio of 0.6. If the monitoring microprocessordetects a cell imbalance, that is, calculates a ratio R substantiallyhigher or lower than the balance ratio of 0.6, operation of the battery600 (i.e., charging and/or discharging) is interrupted or changed. Insome constructions and in some aspects, operation of the battery 600 isinterrupted or changed when the ratio R is not included within the rangeof approximately 0.55 to approximately 0.65.

FIGS. 26 and 27 are a graphs which illustrates an example ofapproximately when an imbalance occurs within the battery 600 and howthe ratio R deviates from its balanced ratio during this occurrence. Inthis example, each cell 605 a-e has a nominal voltage of approximately 4V, and the balanced ratio for ratio R is approximately 0.6 or 60.0%.

In the illustrated construction, axis 700 represents time in seconds,axis 705 represents voltage in volts, and axis 710 represents a ratio ora percentage in volts/volts. Line 715 a represents the voltage of cell605 a over time, line 715 b represents the voltage of cell 605 b overtime, and line 715 c represents the voltage of cell 605 c over time.Line 715 d represents the voltage of cell 605 d over time, line 715 erepresents the voltage of cell 605 e over time, and line 720 representsthe ratio R over time.

In the illustrated example, an imbalance (represented on the graph bynumeral 725) occurs approximately at 86 seconds. The imbalance 725 iscaused by cell 605 e, which is included with group 615. At this time(t=86 s), the ratio 720 begins to decrease or deviate from the balancedratio of 0.6 (i.e., 60%). Since the ratio 720 is decreasing, it can bedetermined that the imbalanced cell is within group 615. When the ratioR approaches 55.0% at approximately 91 seconds (indicated in FIG. 28 bythe numeral 730), the voltage of cell 605 e is approximately 1 V. Insome constructions, the monitoring microprocessor detects that the ratioR has fallen to approximately 55.0% and then terminates operation of thebattery 600 in order to avoid further discharge of cell 605 e.

In some constructions, the monitoring microprocessor monitors thevoltage of each battery cell instead of using a ratiometric method ofmonitoring, such as, for example, the microprocessor 140. As previouslydiscussed, the battery 50 includes the plurality of resistors 260 forproviding voltage measurements of the battery cells 80. The plurality ofresistors 260 are arranged such that the microprocessor 140 can measurethe voltage of each battery cells 80 a-g approximately at the same time.In some constructions, the microprocessor 140 detects an imbalancewithin the battery 50 when one or more cells 80 reach approximately 1 V.

In some constructions and in some aspects, the battery 50 or 600 mayre-balance the cells 80 a-g or 605 a-e when an imbalance has beendetected. In some constructions, the monitoring microprocessor disablesthe battery 50 or 600 (e.g. interrupts battery operation, preventsbattery operation, etc.) when the balanced ratio R is no longer includedwithin an acceptable range. After the battery 50 or 600 is disabled, themonitoring microprocessor determines which cell(s) 80 a-e or 605 a-e isimbalanced (the “low voltage cell”).

In some construction, the monitoring microprocessor activates or turnson the respective transistors, such as, for example, transistors 265a-f, that are electrically connected to those cells 80 a-g or 605-a-ethat are not low in present state of charge (i.e., cells having a higherpresent state of charge than the low voltage cell). The monitoringmicroprocessor begins a controlled discharge of the high present stateof charge cells 80 a-g or 605 a-e. For example, the monitoringmicroprocessor will control the small discharge current that will flowfrom the balanced cells 80 a-e or 605 a-e through the respectivetransistors. The monitoring microprocessor will continue to make voltagemeasurements of the cells 80 a-g or 605 a-e throughout the controlleddischarging process. The monitoring microprocessor will end thecontrolled discharge process when the present state of charge of thehigher state of charge cells 80 a-g or 605 a-e is reduced to beapproximately equal to the previously low voltage cell.

In some constructions, the monitoring microprocessor uses the controlleddischarge process to power an indicator, such as, for example, blinkingall of the LEDs 170 a-d on the fuel gauge 155. In this construction, forexample, the blinking LEDs 170 a-d indicate to an operator or user thatthe battery 50 or 600 is disabled and/or is currently in the process ofre-balancing the cells 80 a-g or 605 a-e.

A further schematic diagram of the battery 50 is schematicallyillustrated in FIG. 28. In some constructions, the circuit 130 includesan electrical component such as, for example, an identification resistor750, and the identification resistor 750 can have a set resistance. Inother constructions, the electrical component may be a capacitor, aninductor, a transistor, a semiconducting element, an electrical circuitor another component having a resistance or capable of sending anelectrical signal such as, for example, a microprocessor, a digitallogic component and the like. In the illustrated construction, theresistance value of the identification resistor 750 can be chosen basedon characteristics of the battery 50, such as the nominal voltage andthe chemistry of the battery cells 80. A sense terminal 120 canelectrically connect to the identification resistor 750.

The battery 50, shown schematically in FIG. 28, can electrically connectto an electrical device, such as a battery charger 820 (also shownschematically) to receive or transfer power. The battery charger 820 caninclude a positive terminal 825, a negative terminal 828 and a senseterminal 830. Each terminal 820, 828, 830 of the battery charger 820 canelectrically connect to the corresponding terminal 110, 115, 120(respectively), of the battery 50. The battery charger 820 also caninclude a circuit having electrical components, such as, for example, afirst resistor 835, a second resistor 840, a solid-state electronicdevice or semiconductor 855, a comparator 860 and a processor ormicrocontroller (not shown). In some constructions, the semiconductor855 can include a transistor capable of operating in saturation or an“ON” state and capable of operating in cut-off or an “OFF” state. Insome constructions, the comparator 860 can be a dedicated voltagemonitoring device, a microprocessor or a processing unit. In otherconstructions, the comparator 860 can be included in the microcontroller(not shown).

In some constructions, the microcontroller (not shown) can be programmedto identify the resistance value of the electrical component in thebattery 50, such as the identification resistor 750. The microcontrollercan also be programmed to determine one or more characteristics of thebattery 50, such as, for example, the battery chemistry and the nominalvoltage of the battery 50. As previously mentioned, the resistance valueof the identification resistor 750 may correspond to a dedicated valueassociated with one or more certain battery characteristics. Forexample, the resistance value of the identification resistor 750 can beincluded in a range of resistance values corresponding to the chemistryand to the nominal voltage of the battery 50.

In some constructions, the microcontroller can be programmed torecognize a plurality of resistance ranges of the identificationresistor 750. In these constructions, each range corresponds to onebattery chemistry, such as, for example, NiCd, NiMH, Li-ion, and thelike. In some constructions, the microcontroller can recognizeadditional resistance ranges, each corresponding to another batterychemistry or another battery characteristic.

In some constructions, the microcontroller can be programmed torecognize a plurality of voltage ranges. The voltages included in thevoltage ranges can be dependent on or correspond to the resistance valueof the identification resistor 750, such that the microcontroller candetermine the value of the resistor 750 based on the measured voltage.

In some constructions, the resistance value of the identificationresistor 750 can be further chosen to be unique for each possiblenominal voltage value of the battery 50. For example, in one range ofresistance values, a first dedicated resistance value can correspond toa nominal voltage of 21 V, a second dedicated resistance value cancorrespond to a nominal voltage of 16.8 V, and a third dedicatedresistance value can correspond to a nominal voltage of 12.6 V. In someconstructions, there can be more or fewer dedicated resistance values,each corresponding to a possible nominal voltage of the battery 50associated with the resistance range.

In an exemplary implementation, the battery 50 electrically connects tothe battery charger 820. To identify a first battery characteristic, thesemiconductor 855 switches to the “ON” state under the control ofadditional circuitry (not shown). When the semiconductor 855 is in the“ON” state, the identification resistor 750 and resistors 835 and 840create a voltage divider network. The network establishes a voltageV_(A) at a first reference point 875. If the resistance value of theresistor 840 is significantly lower than the resistance value of theresistor 835, then the voltage V_(A) will be dependent upon theresistance values of the identification resistor 750 and the resistor840. In this implementation, the voltage V_(A) is in a range determinedby the resistance value of the identification resistor 750. Themicrocontroller (not shown) measures the voltage V_(A) at the firstreference point 875 and determines the resistance value of theidentification resistor 750 based on the voltage V_(A). In someconstructions, the microcontroller compares the voltage V_(A) to aplurality of voltage ranges to determine the battery characteristic.

In some constructions, the first battery characteristic to be identifiedcan include the battery chemistry. For example, any resistance valuebelow 150 k ohms may indicate that the battery 50 has a chemistry ofNiCd or NiMH, and any resistance value approximately 150 k ohms or abovemay indicate that the battery 50 has a chemistry of Li or Li-ion. Oncethe microcontroller determines and identifies the chemistry of thebattery 50, an appropriate charging algorithm or method may be selected.In other constructions, there are more resistance ranges which eachcorrespond to another battery chemistry than in the above example.

Continuing with the exemplary implementation, to identify a secondbattery characteristic, the semiconductor 855 switches to the “OFF”state under the control of the additional circuitry. When thesemiconductor 855 switches to the “OFF” state, the identificationresistor 750 and the resistor 835 create a voltage divider network. Thevoltage V_(A) at the first reference point 875 is now determined by theresistance values of the identification resistor 750 and the resistor835. The resistance value of the identification resistor 750 is chosensuch that, when the voltage V_(BATT) at a second reference point 880substantially equals the nominal voltage of the battery 50, the voltageV_(A) at the first reference point 875 substantially equals a voltageV_(REF) at a third reference point 885. If the voltage V_(A) at thefirst reference point 875 exceeds the fixed voltage V_(REF) at the thirdreference point 885, an output V_(OUT) of the comparator 860 changesstate. In some constructions, the output V_(OUT) can be used toterminate charging or to serve as an indicator to commence additionalfunctions, such as a maintenance routine, an equalization routine, adischarging function, additional charging schemes, and the like. In someconstructions, voltage V_(REF) can be a fixed reference voltage.

In some constructions, the second battery characteristic to beidentified can include a nominal voltage of the battery 50. For example,a general equation for calculating the resistance value for theidentification resistor 750 can be:$R_{100} = \frac{V_{REF} \cdot R_{135}}{V_{BATT} - V_{REF}}$wherein R₁₀₀ is the resistance value of the identification resistor 750,R₁₃₅ is the resistance value of the resistor 835, V_(BATT) is thenominal voltage of the battery 50 and V_(REF) is a fixed voltage, suchas, for example, approximately 2.5 V. For example, in the range ofresistance values for the Li-ion chemistry (set forth above), aresistance value of approximately 150 k ohms for the identificationresistor 750 can correspond to a nominal voltage of approximately 21 V,a resistance value of approximately 194 k ohms can correspond to anominal voltage of approximately 16.8 V, and a resistance value ofapproximately 274.7 k ohms can correspond to a nominal voltage ofapproximately 12.6 V. In other constructions, more or fewer dedicatedresistance values may correspond to additional or different battery packnominal voltage values.

In the illustrated construction, both the identification resistor 750and the third reference point 885 may be situated on the “high” side ofa current sense resistor 890. Positioning the identification resistor750 and the third reference point 885 in this manner can reduce anyrelative voltage fluctuations between V_(A) and V_(REF) when a chargingcurrent is present. Voltage fluctuations may appear in voltage V_(A) ifthe identification resistor 750 and the third reference point 885 werereferenced to ground 895 and a charging current was applied to thebattery 50.

In some constructions, the battery charger 820 can also include acharger control function. As previously discussed, when the voltageV_(A) substantially equals the voltage V_(REF) (indicative of voltageV_(BATT) equaling the nominal voltage of battery 50), the output V_(OUT)of the comparator 860 changes state. In some constructions, the chargingcurrent is no longer supplied to the battery 50 when the output V_(OUT)of the comparator 860 changes state. Once the charging current isinterrupted, the battery voltage V_(BATT) begins to decrease. Whenvoltage V_(BATT) reaches a low threshold, the output V_(OUT) of thecomparator 860 changes state again. In some constructions, the lowthreshold of voltage V_(BATT) is determined by a resistance value of ahysteresis resistor 898. The charging current is reestablished once theoutput V_(OUT) of the comparator 860 changes state again. In someconstructions, this cycle repeats for a predefined amount of time asdetermined by the microcontroller or repeats for a certain amount ofstate changes made by the comparator 860. In some constructions, thiscycle repeats until the battery 50 is removed from the battery charger820.

In some constructions and in some aspects, the circuit 130 of thebattery 50 can also indicate one or more battery characteristics. Insome constructions, the battery characteristics include, for example, anominal voltage and a temperature of the battery 50. The circuit 130includes an electrical identification component or identificationresistor 910, a temperature-sensing device or thermistor 914, a firstcurrent-limiting device or protection diode 918, a secondcurrent-limiting device or protection diode 922 and a capacitor 926. Theidentification resistor 910 has a set resistance value which correspondsto one or more certain battery characteristics. In some constructions,the resistance value of the identification resistor 910 corresponds withthe nominal voltage of the battery 50 or the battery cell 80. In someconstructions, the resistance value corresponds with the chemistry ofthe battery 50. In some constructions, the resistance value correspondswith two or more battery characteristics or corresponds with differentbattery characteristic(s). The resistance value of the thermistor 914 isindicative of the temperature of the battery cell 80 and changes as thetemperature of the battery cell 80 changes. A sense terminal 930electrically connects to the circuit 130.

The battery 50, shown schematically in FIG. 29, electrically connects toan electrical device, such as a battery charger 942 (also shownschematically). The battery charger 942 includes a positive terminal946, a negative terminal 950 and a sense terminal 954. In a mannersimilar to the battery 50 and battery charger 820 illustrated in FIG.28, the positive terminal 934, the negative terminal 938 and the senseterminal 930 of the battery 50 electrically connect to the positiveterminal 946, the negative terminal 950 and the sense terminal 954,respectively, of the battery charger 942. The battery charger 942 alsoincludes control circuitry, such as a control device, processor,microcontroller or controller 958 and an electrical component orresistor 962.

The operation of the battery 50 and battery charger 942 will bediscussed with reference to FIGS. 29 and 30A-B. In some constructions,when the battery 50 electrically connects to the battery charger 942 andthe capacitor 926 is initially discharged, the controller 958 increasesa voltage V_(A) at a first reference point 964 to approximately a firstthreshold. In some constructions, the first threshold is approximately 5V. As shown in FIG. 30A, the controller 958 increases the voltage V_(A)to the first threshold at approximately a time T₁.

When the first threshold is applied to the first reference point 964, afirst current path is established within the battery 50 and batterycharger 942. The first current path includes the resistor 962, thecapacitor 926, the first diode 918 and the identification resistor 910.Once the voltage V_(A) is raised to approximately the first threshold,the controller 958 measures the voltage V_(OUT) at a second referencepoint 966. The voltage V_(OUT) at the second reference point 966 quicklyrises to a voltage determined by a voltage divider network comprised ofthe identification resistor 910, the resistor 962 and the forwardvoltage drop across the diode 918. In some constructions, voltageV_(OUT) will range from approximately 0 V to slightly less than voltageV_(A). As shown in FIG. 30B, a rise in the voltage V_(OUT) occursapproximately at a time T₂, and the controller 958 measures the voltageV_(OUT) at approximately the time T₂ or slightly after time T₂. In someconstructions, time T₂ is approximately equal to time T₁. In someconstructions, time T₂ occurs almost immediately after time T₁. Time T₂may be later based on tolerances in measurement.

In one construction, the voltage V_(OUT) measured by the controller 958corresponds to a resistance value for the identification resistor 910.That resistance value corresponds to the nominal voltage of the battery50. In some constructions, as the resistance value of the identificationresistor 910 decreases, the voltage V_(OUT) also decreases.

In the illustrated construction, the voltage V_(OUT) eventually rises toapproximately the voltage V_(A) once the capacitor 926 becomes fullycharged. After the capacitor 926 is fully charged, the controller 958decreases the voltage V_(A) at the first reference point 964 to a secondthreshold. In some constructions, the second threshold is approximately0 V. As shown in FIG. 30A, the controller 958 decreased the voltageV_(A) to the second threshold at approximately a time T₃.

When the second threshold is applied to the first reference point 964, asecond current path is established within the battery 50 and batterycharger 942. The second current path includes the resistor 962, thecapacitor 926, the second diode 922 and the thermistor 914. Once thevoltage V_(A) is lowered to approximately the second threshold, thecontroller 958 measures the voltage V_(OUT) again at the secondreference point 966. The voltage V_(OUT) at the second reference point966 quickly decreases to a voltage determined by a voltage dividernetwork comprised of the thermistor 914, the resistor 962 and theforward voltage drop across diode 922. In some constructions, V_(OUT)will range from approximately 0 V to slightly less than voltage V_(A).As shown in FIG. 30B, a decrease in the voltage V_(OUT) occursapproximately at a time T₄, and the controller 958 measures the voltageV_(OUT) at approximately the time T₄ or slightly after time T₄. In someconstructions, time T₄ is approximately equal to time T₃. In someconstructions, time T₄ occurs almost immediately after time T₃. Time T₄may be later based on tolerances in measurement.

In one construction, the voltage V_(OUT) measured by the controller 958at time T₄ corresponds to a resistance value for the thermistor 914.That resistance value corresponds to the temperature of the battery 50.In some constructions, as the resistance value of the thermistor 914decreases, the voltage V_(OUT) increases.

In some constructions, the capacitor 926 provides a DC blockingfunction. The capacitor 926 prevents existing battery chargers (e.g.,battery chargers which do not recognize newer power tool batterychemistries, such as, for example, the Li or Li-ion chemistries, andwhich do not have the required corresponding charging algorithms forsuch newer chemistries) from being able to charge a battery pack havingthe circuit 130.

An existing power tool battery 968 is schematically illustrated in FIG.31, and a further construction of a battery 970 is schematicallyillustrated in FIG. 32. Referring to FIGS. 31-34, another batterycharging system includes both batteries 968 and 970, an existing batterycharger 972 (shown in FIG. 33) and a battery charger 974 (shown in FIG.34) embodying aspects of the invention.

Referring to FIG. 31, the existing battery 968 includes one or morebattery cells 976 each having a chemistry and providing a nominalvoltage. Typically, the chemistry of the battery cell 976 is lead-acid,NiCd or NiMH. The battery cell 976 includes a positive end 978 and anegative end 980. A positive terminal 982 electrically connects to thepositive end 978 of the cell 976, and a negative terminal 984electrically connects to the negative end 980 of the cell 976.

The battery 968 also includes an electrical component or thermistor 986.The resistance value of the thermistor 986 is indicative of thetemperature of the battery cell 976 and changes as the temperature ofthe battery cell 976 changes. In some constructions, the resistancevalue of the thermistor 986 is included in a first range of resistancevalues. The existing battery charger 972 is capable of identifying aresistance value of the thermistor 986 within this first range andcharge the existing battery 968 accordingly. For example, this firstrange of resistance values includes the resistance values approximatelyequal to and less than 130 k ohms. If the resistance value of thethermistor 986 is not included in the first range of resistance values,the existing battery charger 972 cannot charge the existing battery 968.The existing battery 968 also includes a sense terminal 988 electricallyconnected to the thermistor 986.

As shown in FIG. 32, the battery 970 includes one or more battery cells990 each having a chemistry and providing a nominal voltage of thebattery 970. Typically, the chemistry of the battery cell 990 includes,for example, Li, Li-ion or another Li-based chemistry. The battery cell990 includes a positive end 992 and a negative end 993. A positiveterminal 994 electrically connects to the positive end 992 of the cell990, and a negative terminal 995 electrically connects to the negativeend 993 of the cell 990.

The battery 970 also includes two sense terminals 996 and 997. The firstsense terminal 996 electrically connects to a first electrical componentor an identification resistor 998, and the second sense terminal 997electrically connects to a second electrical component or atemperature-sensing device or thermistor 999. In some constructions, theresistance value of the identification resistor 998 is not included inthe first range of resistance values that can be identified by theexisting battery charger 972. For example, the resistance value of theidentification resistor 998 is approximately equal to or greater than150 k ohms. The resistance value of the thermistor 986 is indicative ofthe temperature of the battery cell 990 and changes as the temperatureof the battery cell 990 changes.

As shown in FIG. 34 and in most constructions, the battery charger 974includes a positive terminal 1001, a negative terminal 1002, a firstsense terminal 1003 and a second sense terminal 1004. The first senseterminal 1003 of the battery charger 974 electrically connects to eitherthe first sense terminal 996 of battery 970 or to the sense terminal 988of the existing battery 968.

As shown in FIG. 33 and in some constructions, the existing batterycharger 972 includes a positive terminal 1005, a negative terminal 1006and a sense terminal 1007. The sense terminal 1007 of the existingbattery charger 972 electrically connects to either the first senseterminal 996 of the battery 970 or to the sense terminal 988 of theexisting battery 968.

When the existing battery 968 electrically connects to the batterycharger 974, the second sense terminal 1004 of the battery charger 974is not electrically connected to any battery terminal. In someconstructions, a control device, microprocessor, microcontroller orcontroller 1008 included in the new battery charger 974 determines theresistance value of the thermistor 986 through the first sense terminal1003 and identifies the battery 968 as having a NiCd or NiMH chemistry.The controller 1008 selects an appropriate charging method or algorithmfor the existing battery 968 based on the chemistry and the temperatureof the battery 968. The battery charger 974 charges the existing battery968 accordingly.

When the battery 970 electrically connects to the battery charger 974,the second sense terminal 1004 of the battery charger 974 electricallyconnects to the second sense terminal 997 of the battery 970. In someconstructions, the controller 1008 determines the resistance value ofthe identification resistor 998 and identifies the battery 970 ashaving, for example, a Li, Li-ion or another Li-based chemistry. Forexample, a resistance value of approximately 150 k ohms or greater forthe identification resistor 998 corresponds to Li, Li-ion or anotherLi-based chemistry.

In some constructions, the resistance value of the identificationresistor 998 is further chosen based on the nominal voltage of thebattery 970. For example, a resistance value of approximately 150 k ohmsfor the identification resistor 998 indicates that the battery 970 has anominal voltage of approximately 21 V. A resistance value ofapproximately 300 k ohms corresponds to a nominal voltage ofapproximately 16.8 V, and a resistance value of approximately 450 k ohmscorresponds to a nominal voltage of approximately 12.6 V. In someconstructions, as the resistance value of the identification resistor998 increases, the nominal voltage of the battery 970 decreases. In someconstructions, the controller 1008 also determines the resistance valueof the thermistor 385. The controller 1008 selects an appropriatecharging method or algorithm for the battery 970 based on its chemistry,nominal voltage and/or temperature. The battery charger 974 charges thebattery 970 accordingly.

When the existing battery 968 is electrically connected to the existingbattery charger 972, the sense terminal 1007 of the battery charger 972electrically connects to the sense terminal 988 of the existing battery968. In some constructions, the microcontroller 1009 included in theexisting battery charger 972 determines the resistance value of thethermistor 986 and identifies the battery 968 as having a NiCd or NiMHchemistry, if the resistance value of the thermistor 986 is included inthe first range of resistance values. The existing battery charger 972determines the temperature of the existing battery 968 based on theresistance value of the thermistor 986 and selects an appropriatecharging method or algorithm for the battery 968 based on itstemperature. The existing battery charger 972 charges the existingbattery 968 accordingly.

When the battery 970 is electrically connected to the existing batterycharger 972, the sense terminal 1007 of the existing battery charger 972electrically connects to the first sense terminal 996 of the battery970. The second sense terminal 997 of the battery 970 is notelectrically connected to any battery charger terminal of the existingbattery charger 972. In some constructions, the microcontroller 1009determines the resistance value of the identification resistor 998. Insome constructions, the resistance value of the identification resistor998 is not included in the first range of resistance values that arerecognized by the microcontroller 1009. Since the microcontroller 1009cannot identify the battery 970, the existing battery charger 972 doesnot implement a charging method or algorithm. The battery 970 iselectronically prevented or “locked-out” from being charged by theexisting battery charger 972.

Another battery 1030 embodying aspects of the invention is illustratedin FIGS. 35-37, 40-41, 48A, 49-52. The battery 1030 can be similar tothe battery 50 illustrated in FIGS. 1-5. For example, the battery 1030can be connectable to an electrical device or equipment, such as, forexample, a cordless power tool 1034 (shown in FIG. 48A) to selectivelypower the power tool 1034. The battery 1030 can be removable from thepower tool 1034 and can be rechargeable by a battery charger 1038 (shownin FIGS. 40-44).

As shown in FIGS. 35-37, the battery 1030 can include a housing 1042 andat least one rechargeable battery cell 1046 (schematically illustratedin FIG. 41) supported by the housing 1042. In the illustratedconstruction, the battery 1030 can be a 18 V battery pack including fiveapproximately 3.6 V battery cells 1046 (one shown) connected in seriesor can be a 21 V battery pack including five approximately 4.2V batterycells 1046 (one shown) connected in series. In other constructions (notshown), the battery 1030 may have another nominal battery voltage, suchas, for example, 9.6 V, 12 V, 14.4 V, 24 V, 28 V, and the like, to powerthe electrical equipment and be charged by the battery charger 1038. Itshould be understood that, in other constructions (not shown), thebattery cells 1046 can have a different nominal cell voltage and/or maybe connected in another configuration, such as, for example, in parallelor in a parallel/series combination.

The battery cell 1046 can be any rechargeable battery cell chemistrytype, such as, for example, nickel cadmium (NiCd), nickel-metal hydride(NiMH), Lithium (Li), Lithium-ion (Li-ion), other Lithium-basedchemistry, other rechargeable battery cell chemistry, etc. In theillustrated construction, the battery cells 1046 are Li-ion batterycells.

The housing 1042 can provide a support portion 1050 for supporting thebattery 1030 on an electrical device, such as the power tool 1034 or thebattery charger 1038. In the illustrated construction, the supportportion 1050 can provide a C-shaped cross section (see FIG. 37) which isconnectable to a complementary T-shaped shaped cross section supportportion on the electrical device. As shown in FIGS. 35-37, the supportportion 1050 can include rails 1054 extending along a support axis 1058and defining grooves 1062. An intermediate ridge 1066 can also beprovided to engage with a surface of the electrical device supportportion. Recesses 1070 (see FIGS. 35-36) can be defined in the ridge1066 so that the ridge 1066 has laterally-outwardly extended portions1072.

The battery 1030 can also include (see FIGS. 35-37) a locking assembly1074 operable to lock the battery 1030 to an electrical device, such as,for example, to the power tool 1034 and/or to a battery charger 1038. Insome constructions, the locking assembly 1034 can include lockingmembers 1078 which are movable between a locked position, in which thelocking members 1078 engage a corresponding locking member on theelectrical device to lock the battery 1030 to the electrical device, andan unlocked position. The locking assembly 1074 can also includeactuators 1082 for moving the locking members 1078 between the lockedposition and the unlocked position. Biasing members (not shown) can biasthe locking members 1078 toward the locked position.

The battery 1030 can also include (see FIGS. 35-39 and 41) a terminalassembly 1086 operable to electrically connect the battery cells 1046 toa circuit in the electrical device. The terminal assembly 1086 caninclude (see FIGS. 35-37) a terminal housing 1090 provided by thehousing 1042. In the illustrated construction and in some aspects, awindow or opening 1094 can be provided in the terminal housing 1090. Theterminal assembly 1086 can include (see FIGS. 35, 37-39 and 41) apositive battery terminal 1098, a ground terminal 1102, a first senseterminal 1106 and a second sense terminal 1110. As schematicallyillustrated in FIG. 41, the terminals 1098 and 1102 are connected to theopposite ends of the cell or series of cells 1046.

The sense terminals 1106 and 1110 can be connected to electricalcomponents 1114 and 1118, respectively, which are connected in thecircuit of the battery 1030. The sense terminals 1106 and 1110 cancommunicate information regarding the battery 1030 to an electricaldevice. For example, one electrical component, such as the electricalcomponent 1114, connected to the sense terminal 1106 may be anidentification component, such as a resistor, to communicate theidentification of a characteristic of the battery 1030, such as, forexample, the chemistry of the battery cells 1046, the nominal voltage ofthe battery 1030, etc. The other electrical component, such as theelectrical component 1118, connected to the sense terminal 1110 may be atemperature-sensing device or thermistor to communicate the temperatureof the battery 1030 and/or of the battery cell(s) 1046.

In other constructions, the electrical components 1114 and 1118 can beother suitable electrical components capable of generating an electricalsignal such as, for example, a microprocessor, a controller, digitallogic components, and the like, or the components 1114 and 1118 can beother suitable passive electrical components such as, for example,resistors, capacitors, inductors, diodes, and the like.

It should be understood that, in other constructions (not shown), theelectrical components 1114 and 1118 may be other types of electricalcomponents and may communicate other characteristics or informationabout the battery 1030 and/or of the battery cell(s) 1046. It shouldalso be understood that “communication” and “communicate”, as used withrespect to the electrical components 1114 and 1118, may also encompassthe electrical component(s) 1114 and/or 1118 having or being in acondition or state which is sensed by a sensor or device capable ofdetermining the condition or state of the electrical component(s) 1114and/or 1118.

As shown in FIG. 39, the terminals 1098, 1102 and 1106 can be orientedin planes P₁, P₂ and P₃, respectively, which are substantially parallelto one another. The terminal 1110 can be oriented in a plane P₄ which isoriented to be non-parallel to at least one of, and, in the illustratedconstruction, to all of the other planes P₁, P₂ and P₃ In oneconstruction, the plane P₄ can be normal to the planes P₁, P₂ and P₃.The terminals 1098, 1102, 1106 and 1110 can extend along respective axesA₁, A₂, A₃ and A₄, and, in the illustrated construction, the terminalaxes A₁, A₂, A₃ and A₄ are parallel to (see FIGS. 35 and 37) the supportaxis 1058.

As shown in FIGS. 40-44, the battery charger 1038 embodying aspects ofthe invention can be connectable to the battery 1030 (as shown in FIG.40) and can be operable to charge the battery 1030. The battery charger1038 can include a charger housing 1122 and a charging circuit 1126(schematically illustrated in FIG. 41) supported by the housing 1122 andconnectable to a power source (not shown). The charging circuit 1126 canbe connectable to the terminal assembly 1086 of the battery 1030(schematically illustrated in FIG. 41) and can be operable to transferpower to the battery 1030 to charge the battery cell(s) 1046.

In some constructions and in some aspects, the charging circuit 1126 canoperate to charge the battery 1030 in a manner similar to that describedin U.S. Pat. No. 6,456,035, issued Sep. 24, 2002, and U.S. Pat. No.6,222,343, issued Apr. 24, 2001, which are hereby incorporated byreference. In other constructions, the charging circuit 1126 can operateto charge the battery 1030 in a manner similar to that described inprior filed U.S. provisional application Ser. No. 60/440,692 filed Jan.17, 2003, the entire contents of which are hereby incorporated byreference.

As shown in FIGS. 42-44, the housing 1122 can provide a battery supportportion 1130 for supporting the battery 1030. The support portion 1130can have (see FIG. 42) a generally T-shaped cross section which can becomplementary to the C-shaped cross section of the support portion 1050of the battery 1030. The support portion 1130 can include (see FIGS.42-44) rails 1134 which extend along a support axis 1138 and whichdefine grooves 1142. The support portion 1130 can also include a surface1146 which is engageable with the ridge 1066.

Projections or ribs 1150 can extend from the surface 1146. When thebattery 1030 is positioned on the support portion 1130, the ribs 1150can be generally laterally aligned with the locking members 1078 tomaintain the locking members 1078 in the locking position. In oneconstructions, the ribs 1150 are lowered to ensure that the ribs 1150 donot engage with the ridge 1066 on the support portion 1050 of thebattery 1030, which would prevent the battery 1030 from being connectedto the battery charger 1038.

The battery charger 1038 can also include (see FIGS. 41-47) a terminalassembly 1154 operable to electrically connect the charging circuit 1126to the terminal assembly 1086 of the battery 1030 (as schematicallyillustrated in FIG. 41). As shown in FIGS. 42-44 and 46-47, the terminalassembly 1154 can include a terminal housing 1158 provided by thesupport portion 1130. The terminal assembly 1154 also can include (seeFIGS. 41-47) a positive terminal 1162, a negative terminal 1166, a firstsense terminal 1170 and a second sense terminal 1174. The chargerterminals 1162, 1166, 1170 and 1174 can be connectable to the batteryterminals 1098, 1102, 1106 and 1110, respectively (as schematicallyillustrated in FIG. 41).

The charger terminals 1162, 1166, 1170 and 1174 can be connected to thecharging circuit 1126. The charging circuit 1126 can include amicrocontroller 1178 for controlling charging of the battery 1030. Thecontroller 1178 is operable to communicate with or sense the conditionor state of the electrical components 1114 and 1118 of the battery 1030to identify one or more characteristics and/or conditions of the battery1030, such as, for example, the nominal voltage of the battery 1030, thechemistry of the battery cell(s) 1046, the temperature of the battery1030 and/or of the battery cell(s) 1046, etc. Based upon determinationsmade by the controller 1178, the controller 1178 can control thecharging circuit 1126 to properly charge the battery 1030.

As shown in FIGS. 35, 37-39, the battery terminals 1098, 1102 and 1106can be male blade terminals. As shown in FIG. 42, the charger terminals1162, 1166 and 1170 can be female terminals operable to receive the maleblade terminals 1098, 1102 and 1106. The battery terminal 1110 (seeFIGS. 35-39) and the charger terminal 1174 (see FIGS. 42-44) can providea cantilever spring-type engagement. In the illustrated construction(see FIGS. 42-44), the charger terminal 1174 can extend generallyperpendicularly to the support axis 1138 to provide a sliding engagementand contact with the battery terminal 1110.

The battery 1030 can be connectable to electrical equipment, such as,for example, the power tool 1034 (shown in FIG. 48A), to power the tool1034. The power tool 1034 includes a housing 1182 supporting an electricmotor 1184 (schematically illustrated) selectively powered by thebattery 1030. The housing 1182 can provide (see FIG. 48B) a supportportion 1186 on which the battery 1030 can be supported. The supportportion 1186 can have a generally T-shaped cross section which can becomplementary to the C-shaped cross section of the support portion 1050of the battery 1030. The support portion 1186 also can define lockingrecesses 1188 (one shown) in which the locking members 1078 areengageable to lock the battery 1030 to the power tool 1034.

The power tool 1034 can also include a terminal assembly 1190 (partiallyshown in FIG. 48B) connectable to the terminal assembly 1086 of thebattery 1030 so that power is transferable from the battery 1030 to thepower tool 1034. In the illustrated construction, the terminal assembly1190 can include a positive terminal 1194 and a negative terminal 1198which are connected to the terminals 1098 and 1102, respectively, of thebattery 1030.

It should be understood that, in other constructions (not shown), theterminal assembly 1190 may include additional terminals (not shown)which are connectable to the sense terminals 1106 and/or 1110 so thatinformation regarding the battery 1030, such as, for example, one ormore characteristics of the battery 1030 and/or conditions of thebattery 1030, may be communicated to or sensed by the power tool 1034.In such constructions, the power tool 1034 may include a controller (notshown) to determine the communicated or sensed information regarding thebattery 1030 and to control operation of the power tool 1034 based onthis information.

An alternative construction of a battery 1030A embodying aspects of theinvention is illustrated in FIGS. 53-56. Common elements are identifiedby the same reference number “A”.

As shown in FIGS. 53-56, the battery 1030A can include a housing 1042Asupporting one or more cells (not shown but similar to the cells 1046).The battery 1030A can include a support portion 1050A which has (seeFIG. 56) a generally C-shaped cross section which can be complementaryto (see FIG. 42) the support portion 1130 of the battery charger 1038and to (see FIG. 48B) the support portion 1186 of the power tool 1034 sothat the battery 1030A is connectable to the battery charger 1038 andthe power tool 1034.

As shown in FIGS. 53-56, the support portion 1050A can include the ridge1066A. As shown in FIG. 55, the ridge 1066A can extend farther to onelateral side (the lower lateral side in FIG. 55) to provide alaterally-outwardly extended portion 1072A.

For some constructions and for some aspects, additional independentfeatures, structure and operation of the battery 1030A are described inmore detail above.

When the battery 1030A is positioned on the support portion 1130 of thebattery charger 1038, the lowered ribs 1150 (shown in FIG. 42) do notengage with (see FIG. 55) the extended portion 1072A of the ridge 1066Aon the support portion 1050A of the battery 1030A so that the battery1030A is not prevented from being connected to the battery charger 1038.

FIGS. 57-61 illustrate a prior art battery 1230. The battery 1230 caninclude a housing 1242 and at least one rechargeable battery cell 1246(schematically illustrated in FIG. 61) supported by the housing 1242. Inthe illustrated construction, the battery 1230 is an 18V battery packincluding 15 approximately 1.2 V battery cells 1246 connected in series.In other constructions (not shown), the battery 1230 may have anothernominal voltage, such as, for example, 9.6V, 12V, 14.4V, 24V, etc., topower the electrical equipment and be charged by the battery charger1038. It should be understood that, in other constructions (not shown),the battery cells 1246 may have a different nominal cell voltage and/ormay be connected in another configuration, such as, for example, inparallel or in a parallel series combination. The battery cells 1246 maybe a rechargeable battery cell chemistry type, such as, for example,NiCd or NiMH.

As shown in FIGS. 57-60, the housing 1242 can provide a support portion1250 for supporting the battery 1230 on an electrical device, such asthe power tool 1034 (shown in FIG. 48) or the battery charger 1038(shown in FIG. 42). In the illustrated construction, the support portion1250 can provide (see FIG. 60) a C-shaped cross section which isconnectable to a complementary T-shaped cross section support portion onthe electrical device (the support portion 1186 on the power tool 1034(shown in FIG. 48B) and/or the battery support portion 1130 on thebattery charger 1038 (shown in FIG. 42)). As shown in FIGS. 57-60, thesupport portion 1250 can include rails 1254 extending along a supportaxis 1258 and defining grooves 1262, an intermediate ridge 1266 can beprovided to engage with a surface of the electrical device supportportion. The ridge 1266 can have substantially linear and uninterruptedlateral surfaces 1272. The ridge 1266 does not providelaterally-outwardly extended portions (like the extended portions 1072of the battery 1030 (shown in FIG. 36) or the extended portion 1072A ofthe battery 1030A (shown in FIG. 55)).

The battery 1230 also can include (see FIGS. 57-60) a locking assembly1274 operable to lock the battery 1230 to an electrical device, such as,for example, to the power tool 1034 (shown in FIG. 48A) and/or to abattery charger. The locking assembly 1274 can include (see FIGS. 57-60)locking members 1278 which are moveable between a locked position, inwhich the locking members 1278 can engage a corresponding locking memberon the electrical device (such as the locking recess 1188 on the powertool 1034) to lock the battery 1230 to the electrical device, in anunlocked position. The locking assembly 1274 can also include actuators1282 for moving the locking members 1278 between the locked position andthe unlocked position. Biasing members (not shown) can bias the lockingmembers 1278 toward the locked position.

The battery 1230 can include (see FIGS. 58 and 60) a terminal assembly1286 operable to electrically connect battery cells 1246 to a circuit inthe electrical device. The terminal assembly 1286 includes a terminalhousing 1290 provided by the housing 1242. The terminal assembly 1286can include a positive battery terminal 1298, a ground terminal 1302,and a sense terminal 1306. As shown in FIGS. 58 and 60, the terminals1298, 1302 and 1306 can be oriented in planes which are substantiallyparallel to one another and can extend along respective axes which areparallel to the support axis 1258.

As schematically illustrated in FIG. 61, the terminals 1298 and 1302 canbe connected to the opposite ends of the cell or series of cells 1246.The sense terminal 1306 can be connected to an electrical component 1314which is connected in the circuit of the battery 1230. In theillustrated construction, the electrical component 1314 can be atemperature-sensing device or thermistor to communicate the temperatureof the battery 1230 and/or of the battery cells 1246.

As schematically illustrated in FIG. 61, the battery 1230 can beconnectable to the battery charger 1038, and the battery charger 1038can be operable to charge the battery 1230. The battery terminals 1298,1302 and 1306 can be connectable to three of the charger terminals 1162,1166 and 1170, respectively. The microcontroller 1178 can identify thebattery 1230 (or determines that the battery 1230 is not a battery 1030or a battery 1030A) and identify the condition of the electricalcomponent 1314 or thermistor to sense the temperature of the battery1230. The microcontroller 1178 can control charging of the battery 1230.

The battery 1230 can be supported on the support portion 1130 of thebattery charger 1038. The ribs 1150 (shown in FIG. 42) may not engagethe ridge 1266 on the support portion 1250 of the battery 1230 (shown inFIGS. 57-60) so that the battery 1230 is not prevented from beingconnected to the battery charger 1038.

The battery 1230 can be connectable to electrical equipment, such as,for example, the power tool 1034 (shown in FIG. 48A), to power the powertool 1034. The battery 1230 can be supported on the support portion 1186of the power tool 1034 (shown in FIG. 48B) and can be connectable to themotor 1184 (schematically illustrated in FIG. 48A) to power the motor1184.

FIGS. 62-65 illustrate another battery charger 1338. The battery charger1338 can include a charger housing 1342 and a charging circuit 1346(schematically illustrated in FIG. 65) supported by the housing 1342 andconnectable to a power source (not shown). The charging circuit 1346 canbe connectable to the terminal assembly 1286 of the battery 1230 and canbe operable to transfer power to the battery 1230 to charge the batterycells 1246.

As shown in FIGS. 62-64, the housing 1342 can provide a battery supportportion 1350 for supporting the battery 1230. The support portion 1350can have (see FIG. 62) a generally T-shaped cross section which may becomplementary to the C-shaped cross section of the support portion 1250of the battery 1230 (shown in FIG. 60). The support portion 1350 caninclude (see FIGS. 62-64) rails 1354 which extend along a support axis1358 and which define grooves 1362. The support portion 1350 can includea surface 1366 which can be engageable with the ridge 1266.

Projections or ribs 1370 can extend from the surface 1366. The ribs 1370can extend farther from the surface 1366 than (see FIGS. 43-44) the ribs1150 extend from the surface 1146 of the battery charger 1038. When thebattery 1230 is supported on the support portion 1350, the ribs 1370 canslide along (see FIG. 59) the lateral edges of the ridge 1266 so thatthe battery 1230 is connectable to the battery charger 1338. The ridge1266 of the battery 1230 may be more narrow in a lateral direction than(see FIG. 36) the ridge 1066 of the battery 1030 and may not include theextended portions 1072.

As shown in FIGS. 62-65, the battery charger 1338 can include a terminalassembly 1374 operable to electrically connect the charging circuit 1346to the terminal assembly 1286 of the battery 1230. The terminal assembly1374 can include (see FIGS. 62-64) a terminal housing 1378 provided bythe support portion 1350. The terminal assembly 1374 also can include apositive terminal 1382, a negative terminal 1386 and a sense terminal1390. As schematically illustrated in FIG. 65, the charger terminals,1382, 1386 and 1390 can be connectable to the battery terminals 1298,1302 and 1306, respectively.

The charging circuit 1346 can include a microcontroller 1394 forcontrolling charging of the battery 1230. The controller 1394 candetermine the temperature of the battery 1230 by sensing the conditionof the electrical component 1314 or thermistor. Based upon thedeterminations made by the controller 1394, the controller 1394 cancontrol the charging circuit 1346 to properly charge the battery 1230.

In an exemplary implementation, if a user attempts to connect thebattery 1030 to the battery charger 1338, a portion of the batterycharger 1338, such as the upwardly-extended ribs 1370 (shown in FIG.62), may prevent the battery 1030 from being connected to the batterycharger 1338. As the battery 1030 is positioned on the support portion1350, the ribs 1370 engage the laterally-wider extended portions 1072 ofthe ridge 1066 of the support portion 1050 of the battery 1030 (shown inFIG. 36) to prevent the battery 1030 from being fully connected to thebattery charger 1338. The ribs 1370 are positioned on the supportportion 1350 so that the terminal assembly 1086 of the battery 1030 isnot connectable to the terminal assembly 1374 of the charger 1338.

In some aspects, the invention provides a battery, such as the battery1030 or 1030A, and/or a battery charger, such as the battery charger1038, having additional communication or sense path(s). In some aspects,the invention provides a charger, such as the charger 1038, which iscapable of charging battery packs having additional communication orsense path(s), such as the battery 1030 or 1030A, and batteries nothaving the additional communication or sense path(s), such as thebattery 1230. In some aspects, the invention provides a “mechanicallockout” to prevent a battery, such as the battery 1030 or 1030A, frombeing connected to a charger, such as an existing charger 1338, whilethe battery, such as the battery 1030 or 1030A, may be used with acorresponding existing electrical device, such as the power tool 1034.

The constructions described above and illustrated in the figures arepresented by way of example only and are not intended as a limitationupon the concepts and principles of the present invention. As such, itwill be appreciated by one having ordinary skill in the art that variouschanges in the elements and their configuration and arrangement arepossible without departing from the spirit and scope of the presentinvention as set forth in the appended claims.

1. A method of conducting an operation including a battery pack, saidmethod comprising the acts of: monitoring a first battery pack conditionat a first monitoring rate; determining when a second battery packcondition reaches a threshold; after the second battery pack conditionreaches the threshold, monitoring the first battery pack condition at asecond monitoring rate, the second monitoring rate being different thanthe first monitoring rate.
 2. The method as set forth in claim 1 whereinthe first monitoring act is performed when the second battery packcondition is at least one of equal to and greater than the threshold. 3.The method as set forth in claim 1 wherein the second monitoring act isperformed when the second battery pack condition is at least one ofequal to and less than the threshold.
 4. The method as set forth inclaim 1 wherein the first battery pack condition is a battery packvoltage.
 5. The method as set forth in claim 1 wherein the secondbattery pack condition is a battery pack voltage.
 6. The method as setforth in claim 1 wherein the first battery pack condition and the secondbattery pack condition are the same battery pack condition.
 7. Themethod as set forth in claim 6 wherein the first battery pack conditionand the second battery pack condition are the battery pack voltage. 8.The method as set forth in claim 1 wherein the first monitoring rate isslower than the second monitoring rate.
 9. The method as set forth inclaim 1 wherein the second monitoring rate is faster than the firstmonitoring rate.
 10. The method as set forth in claim 1 and furthercomprising the act of transferring power between the battery pack and anelectrical device.
 11. The method as set forth in claim 10 wherein thetransferring act includes the act of supplying power from the batterypack to an electrical device to operate the electrical device.
 12. Themethod as set forth in claim 11 and further comprising the acts of:determining when the second battery condition reaches a secondthreshold; and interrupting the supply of power from the battery pack tothe electrical device to interrupt operation of the electrical device.13. The method as set forth in claim 1 wherein the battery pack includesa cell, and wherein the first battery pack condition is a cell voltage.14. The method as set forth in claim 1 wherein the battery pack includesa cell, and wherein the second battery pack condition is a cell voltage.15. The method as set forth in claim 1 and further comprising the act ofconnecting a controller to the battery pack, the controller performingthe monitoring acts and the determining act.
 16. The method as set forthin claim 1 wherein the battery pack is a power tool battery pack, andwherein the method further comprises the act of connecting the batterypack to a power tool.
 17. The method as set forth in claim 1 wherein atleast one of the first monitoring rate and the second monitoring rate isa fixed monitoring rate.
 18. The method as set forth in claim 1 whereinthe first monitoring rate is about 1 measurements/second.
 19. The methodas set forth in claim 18 wherein the second monitoring rate is about 100measurements/second.
 20. The method as set forth in claim 1 wherein atleast one of the first monitoring rate and the second monitoring rate isa variable monitoring rate.
 21. The method as set forth in claim 20 andfurther comprising the act of determining the variable monitoring rate.22. The method as set forth in claim 21 wherein the act of determiningthe variable monitoring rate includes the act of determining thevariable monitoring rate based on at least one of the first battery packcondition and the second battery pack condition.
 23. A battery packcomprising: a housing; a cell having a voltage, power being transferablebetween the cell and the electrical device; a controller operable tocontrol a function of the battery pack, the controller being operablewith a voltage at least one of equal to and greater than an operatingvoltage threshold, the cell being operable to selectively supply voltageto the controller; and a circuit operable to enable the controller tooperate when the voltage supplied by the cell is below the operatingvoltage threshold.
 24. The battery pack as set forth in claim 23 whereinthe circuit is operable to supply voltage to the controller such thatthe voltage supplied to the controller is at least one of equal to andgreater than an operating voltage threshold.
 25. The battery pack as setforth in claim 24 wherein the circuit includes a boost circuit operableto boost the voltage supplied by the cell to at least one of equal toand greater than an operating voltage threshold.
 26. The battery pack asset forth in claim 24 wherein the circuit includes a power sourceoperable to supply voltage to the controller such that the voltagesupplied to the controller is at least one of equal to and greater thanan operating voltage threshold, the power source not being operable tosupply power to the electrical device.
 27. The battery pack as set forthin claim 26 wherein the power source includes a power component operableto supply voltage to the controller such that the voltage supplied tothe controller is at least one of equal to and greater than an operatingvoltage threshold.
 28. The battery pack as set forth in claim 27 whereinthe power component includes a capacitor operable to supply voltage tothe controller such that the voltage supplied to the controller is atleast one of equal to and greater than an operating voltage threshold.29. The battery pack as set forth in claim 27 wherein the powercomponent includes a battery cell operable to supply voltage to thecontroller such that the voltage supplied to the controller is at leastone of equal to and greater than an operating voltage threshold.
 30. Thebattery pack as set forth in claim 23 wherein the circuit includes aswitch operable to selectively interrupt the transfer of power betweenthe cell and the electrical device, the controller being operable tocontrol the switch such that the voltage supplied by the cell to thecontroller is at least one of equal to and greater than an operatingvoltage threshold.
 31. The battery pack as set forth in claim 30 whereinthe switch includes a FET, the controller being operable to control theFET such that the voltage supplied by the cell to the controller is atleast one of equal to and greater than an operating voltage threshold.32. The battery pack as set forth in claim 23 wherein the cell isoperable to supply power to the electrical device to operate theelectrical device.
 33. The battery pack as set forth in claim 32 whereinsaid battery pack is a power tool battery pack, wherein the electricaldevice is a power tool, and wherein the cell is operable to supply powerto the power tool to operate the power tool.
 34. The battery pack as setforth in claim 32 wherein, when the cell is at a low temperature, thesupply of power to the electrical device causes the voltage supplied bythe cell to the controller to be below the operating voltage threshold.35. The battery pack as set forth in claim 34 wherein, when the cell isat a higher temperature, the supply of power to the electrical devicedoes not cause the voltage supplied by the cell to the controller to bebelow the operating voltage threshold.
 36. The battery pack as set forthin claim 32 wherein, when an ambient temperature is a low temperature,the supply of power to the electrical device causes the voltage suppliedby the cell to the controller to be below the operating voltagethreshold.
 37. The battery pack as set forth in claim 36 wherein, whenthe ambient temperature is at a higher temperature, the supply of powerto the electrical device does not cause the voltage supplied by the cellto the controller to be below the operating voltage threshold.
 38. Thebattery pack as set forth in claim 32 wherein a load on the electricaldevice causes the voltage supplied by the cell to the controller to bebelow the operating voltage threshold.
 39. The battery pack as set forthin claim 32 wherein the operating voltage threshold is about 5 volts.40. The battery pack as set forth in claim 32 wherein the operatingvoltage threshold is about 3 volts.
 41. The battery pack as set forth inclaim 33 wherein the function includes interrupting the transfer ofpower between the cell and the electrical device.
 42. The battery packas set forth in claim 41 wherein the cell is operable to supply power tothe electrical device to operate the electrical device, and wherein thefunction includes interrupting the supply of power from the cell to theelectrical device.
 43. The battery pack as set forth in claim 41 whereinthe electrical device is a power tool, and wherein the function includesinterrupting the supply of power from the cell to the power tool.
 44. Amethod for operating a battery pack, the battery pack having a batterypack condition, the battery pack condition having a range, said methodcomprising the acts of: conducting an operation including the batterypack; measuring a first measurement of the battery pack condition;measuring a second measurement of the battery pack condition, at leastone of the first measurement and the second measurement being outside ofthe range; averaging the first measurement and the second measurement toprovide an average measurement; and if the average measurement is withinthe range, continuing the operation including the battery pack.
 45. Themethod as set forth in claim 44 and further comprising the act ofproviding a controller, and wherein the measuring acts and the averagingact are performed by the controller.
 46. The method as set forth inclaim 45 wherein the providing act includes the act of providing thebattery pack including the controller.
 47. The method as set forth inclaim 44 wherein the battery pack condition is a voltage.
 48. The methodas set forth in claim 44 wherein the battery pack condition is atemperature.
 49. The method as set forth in claim 44 and furthercomprising the act of measuring a third measurement of the battery packcondition, and wherein the averaging act includes the act of averagingthe first measurement, the second measurement and the third measurementto provide the average measurement.
 50. The method as set forth in claim44 and further comprising the act of discontinuing the operationincluding the battery pack if the average measurement is outside of therange.
 51. The method as set forth in claim 50 wherein the rangeincludes a range threshold, and wherein the discontinuing act includesthe act of discontinuing the operation if the average measurement is atleast one of equal to and greater than the range threshold.
 52. Themethod as set forth in claim 50 wherein the range includes a rangethreshold, and wherein the discontinuing act includes the act ofdiscontinuing the operation if the average measurement is at least oneof equal to and less than the range threshold.
 53. The method as setforth in claim 44 wherein the conducting act and the continuing actinclude the act of supplying power from the battery pack to anelectrical device to operate the electrical device.
 54. The method asset forth in claim 53 wherein the supplying act includes supplying powerfrom the battery pack to a power tool to operate the power tool.
 55. Themethod as set forth in claim 54 wherein the conducting act includes theact of supplying an in rush current to the power tool, the act ofsupplying the in rush current causing at least one of the firstmeasurement and the second measurement to be outside of the range. 56.The method as set forth in claim 54 wherein the conducting act includesthe act of supplying a speed control signal to the power tool, the actof supplying the speed control signal causing at least one of the firstmeasurement and the second measurement to be outside of the range. 57.The method as set forth in claim 54 wherein the conducting act includesthe act of stalling the power tool, the act of stalling the power toolcausing at least one of the first measurement and the second measurementto be outside of the range.
 58. The method as set forth in claim 44wherein the conducting act and the continuing act include the act ofsupplying power to battery pack to charge the battery pack.
 59. A methodof conducting an operation including a battery pack, said methodcomprising the acts of: monitoring a battery pack condition; andcontrolling a function of the battery pack, the controlling actincluding the acts of when the battery pack condition is in a firstrange, controlling the function with a first response time for thefunction, and when the battery pack condition is in a second range,controlling the function with a second response time for the function,the second response time being different than the first response time.60. The method as set forth in claim 59 and further comprising the actof providing a controller, and wherein the monitoring act and thecontrolling act are performed by the controller.
 61. The method as setforth in claim 60 wherein the providing act includes the act ofproviding the battery pack including the controller.
 62. The method asset forth in claim 59 wherein the battery pack condition is a voltage.63. The method as set forth in claim 59 wherein the battery packcondition is a temperature.
 64. The method as set forth in claim 59wherein the monitoring act includes the acts of measuring a firstmeasurement of the battery pack condition, measuring a secondmeasurement of the battery pack condition, and averaging the firstmeasurement and the second measurement to provide an averagemeasurement.
 65. The method as set forth in claim 64 wherein thecontrolling act includes the acts of when the average measurement is inthe first range, controlling the function with the first response timefor the function, and when the average measurement is in the secondrange, controlling the function with the second response time for thefunction.
 66. The method as set forth in claim 59 and further comprisingthe act of conducting an operation including the battery pack.
 67. Themethod as set forth in claim 66 wherein the function is the act ofdiscontinuing the operation including the battery pack.
 68. The methodas set forth in claim 67 wherein the first range includes a rangethreshold.
 69. The method as set forth in claim 68 wherein thediscontinuing act includes the act of discontinuing the operation if theaverage measurement is at least one of equal to and greater than therange threshold.
 70. The method as set forth in claim 68 wherein thediscontinuing act includes the act of discontinuing the operation if theaverage measurement is at least one of equal to and less than the rangethreshold.
 71. The method as set forth in claim 68 wherein the rangethreshold is between the first range and the second range.
 72. Themethod as set forth in claim 66 wherein the conducting act includes theact of supplying power from the battery pack to an electrical device tooperate the electrical device.
 73. The method as set forth in claim 72wherein the supplying act includes supplying power from the battery packto a power tool to operate the power tool.
 74. The method as set forthin claim 72 wherein the conducting act includes the act of supplying anin rush current to the power tool, the act of supplying the in rushcurrent causing the battery pack condition to be in one of the firstrange and the second range.
 75. The method as set forth in claim 72wherein the conducting act includes the act of supplying a speed controlsignal to the power tool, the act of supplying the speed control signalcausing the battery pack condition to be in one of the first range andthe second range.
 76. The method as set forth in claim 72 wherein theconducting act includes the act of stalling the power tool, the act ofstalling the power tool causing the battery pack condition to be in oneof the first range and the second range.
 77. The method as set forth inclaim 66 wherein the conducting act includes the act of supplying powerto battery pack to charge the battery pack.
 78. The method as set forthin claim 59 wherein the first response time is slower than the secondresponse time.
 79. The method as set forth in claim 59 wherein the firstresponse time is faster than the second response time.
 80. The method asset forth in claim 59 wherein at least one of the first response timeand the second response time is fixed.
 81. The method as set forth inclaim 59 wherein at least one of the first response time and the secondresponse time is variable.
 82. The method as set forth in claim 81 andfurther comprising the act of determining the one of the first responsetime and the second response time.
 83. The method as set forth in claim59 wherein the function includes the act of interrupting the transfer ofpower between the cell and the electrical device.
 84. The method as setforth in claim 83 wherein the cell is operable to supply power to theelectrical device to operate the electrical device, and wherein thefunction includes the act of interrupting the supply of power from thecell to the electrical device.
 85. The method as set forth in claim 83wherein the electrical device is a power tool, and wherein the functionincludes the act of interrupting the supply of power from the cell tothe to the power tool.
 86. A battery pack comprising: a housing; a cellsupported by the housing, power being transferable between the cell andan electrical device; a circuit supported by the housing and operable tocontrol a function of the battery pack; and a heat sink in heat transferrelationship with the circuit and operable to dissipate heat from thecircuit.
 87. The battery pack as set forth in claim 86 wherein thecircuit includes a controller, and wherein the heat sink is in heattransfer relationship with the controller and operable to dissipate heatfrom the controller.
 88. The battery pack as set forth in claim 86wherein the circuit includes a switch operable to interrupt the transferof power between the cell and the electrical device, and wherein theheat sink is in heat transfer relationship with the switch and operableto dissipate heat from the switch.
 89. The battery pack as set forth inclaim 88 wherein the switch includes a FET, and wherein the heat sink isin heat transfer relationship with the FET and operable to dissipateheat from the FET.
 90. The battery pack as set forth in claim 89 whereinthe circuit includes a controller, and wherein the heat sink is in heattransfer relationship with the controller and operable to dissipate heatfrom the controller.
 91. The battery pack as set forth in claim 86wherein the function includes interrupting the transfer of power betweenthe cell and the electrical device.
 92. The battery pack as set forth inclaim 91 wherein the cell is operable to supply power to the electricaldevice to operate the electrical device, and wherein the functionincludes interrupting the supply of power from the cell to theelectrical device.
 93. The battery pack as set forth in claim 91 whereinthe electrical device is a power tool, and wherein the function includesinterrupting the supply of power from the cell to the to the power tool.94. A method of conducting an operation including a battery, the batteryincluding a cell having a voltage, power being transferable between thecell and the electrical device, a controller operable to control afunction of the battery pack, the controller being operable with avoltage at least one of equal to and greater than an operating voltagethreshold, the cell being operable to selectively supply voltage to thecontroller, said method comprising the act of enabling the controller tooperate when the voltage supplied by the cell is below the operatingvoltage threshold.
 95. The method as set forth in claim 94 wherein thebattery includes a circuit operable to supply voltage to the controller,and wherein the enabling act includes the act of, with the circuit,supplying a voltage to the controller such that the voltage supplied tothe controller is at least one of equal to and greater than an operatingvoltage threshold.
 96. The method as set forth in claim 95 wherein thecircuit includes a boost circuit operable to boost the voltage suppliedby the cell, and wherein the supplying act includes boosting the voltagesupplied to the controller by the cell to at least one of equal to andgreater than an operating voltage threshold.
 97. The method as set forthin claim 95 wherein the circuit includes a power source operable tosupply voltage to the controller, the power source not being operable tosupply power to the electrical device, and wherein the supplying actincludes the act of supplying voltage from the power source to thecontroller such that the voltage supplied to the controller is at leastone of equal to and greater than an operating voltage threshold.
 98. Themethod as set forth in claim 97 wherein the power source includes apower component operable to supply voltage to the controller, andwherein the supplying act includes the act of supplying voltage from thepower component to the controller such that the voltage supplied to thecontroller is at least one of equal to and greater than an operatingvoltage threshold.
 99. The method as set forth in claim 98 wherein thepower component includes a capacitor operable to supply voltage to thecontroller, and wherein the supplying act includes the act of supplyingvoltage from the capacitor to the controller such that the voltagesupplied to the controller is at least one of equal to and greater thanan operating voltage threshold.
 100. The method as set forth in claim 98wherein the power component includes a battery cell operable to supplyvoltage to the controller, and wherein the supplying act includes theact of supplying voltage from the battery cell to the controller suchthat the voltage supplied to the controller is at least one of equal toand greater than an operating voltage threshold.
 101. The method as setforth in claim 94 wherein the circuit includes a switch operable toselectively interrupt the transfer of power between the cell and theelectrical device, and wherein the enabling act includes the act ofcontrolling the switch such that the voltage supplied by the cell to thecontroller is at least one of equal to and greater than an operatingvoltage threshold.
 102. The method as set forth in claim 101 wherein theswitch includes a FET, and wherein the enabling act includes the act ofcontrolling the FET such that the voltage supplied by the cell to thecontroller is at least one of equal to and greater than an operatingvoltage threshold.
 103. The method as set forth in claim 94 and furthercomprising the act of supplying power from the cell to the electricaldevice to operate the electrical device.
 104. The method as set forth inclaim 103 wherein said battery pack is a power tool battery pack,wherein the electrical device is a power tool, and wherein the supplyingact includes the act of supplying power from the cell to the power toolto operate the power tool.
 105. The method as set forth in claim 94 andfurther comprising the act of, with the controller, interrupting thetransfer of power between the cell and the electrical device.
 106. Themethod as set forth in claim 105 wherein the cell is operable to supplypower to the electrical device to operate the electrical device, andwherein interrupting act includes the act of interrupting the supply ofpower from the cell to the electrical device.
 107. The method as setforth in claim 105 wherein the electrical device is a power tool, andwherein the interrupting act includes the act of interrupting the supplyof power from the cell to the power tool.